129. Differences between Necessity Verbs

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Different shades of necessity meaning are expressed by different English modal verbs

THE VARIETY OF NECESSITY VERBS

Necessity verbs indicate a pressure to do or be something, different ones indicating different types and strengths of pressure. In the following example, the necessity verb must expresses strong legal pressure on vehicle owners to be in possession of insurance:

(a) Vehicle owners must have insurance.

Necessity verbs in English can be divided into two major types: verbs of the ordinary kind, such as NECESSITATE, and verbs of a more grammatical nature that are sometimes called “modal”: MUST, BE TO, HAVE TO, NEED, SHOULD etc. Verbs of the first kind are considered elsewhere within this blog in 65. Verbs that Mean “Must” or “Can”. Here I wish to examine the modal kind, which seem to differ from each other in particularly subtle and confusing ways.

The meanings of these verbs are all commonly explained in mainstream grammar descriptions. What I hope to offer is a number of novel interpretations that might make the meaning differences slightly easier to understand. For information about other posts within this blog that deal with modal verbs, see 237. Auxiliary Verbs in Professional Communication.

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ANALYSIS OF NECESSITY VERBS

The necessity verbs listed above can be divided into two groups according to whether the necessity begins before the time when they are used, so that it is being relayed, or at the very moment of their use (for more on this distinction, see 238. Using a Verb to Perform its Action). Here is a summary of the possibilities:

The details of this classification are as follows.

1. BE TO

This verb is extensively analysed in a previous post (119. BE Before a “to” Verb). Necessity is only one of its many meanings. Mostly it is necessity created before the moment of utterance. The commonest type is arrangements, as in this example:

(b) A meeting of finance ministers is to be held in Brussels.

This would normally mean that the necessity of the meeting was created earlier by people making an arrangement, which the speaker is merely reporting. No necessity is being created through the words being spoken.

Another previously-created necessity that BE TO can report is that resulting from formal regulations, which MUST also commonly expresses (see below). The following sentence might suggest this if spoken to the staff of an organization:

(c) Visitors are to report to Reception.

Using are to here instead of must makes the necessity sound less dictatorial, perhaps by suggesting it is based on communal agreement.

BE TO can also create necessity at the moment of its use, mainly of the command type. Sentence (c) could be a command – again more gentle than with MUST – if addressed to the public.

To make the negative of BE TO, add not before to. For the past tense, use past forms of BE.

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2. HAVE TO

This combination nearly always expresses necessity. The primary use is to relay a previously-established necessity without suggesting how it may have come about:

(d) The children cannot attend because they have to do homework.

It is not clear here what previously caused the necessity: it may have been a school command or regulation, or a parental command, or the children themselves driven by a belief in homework. Using must instead of have to would more strongly suggest that an order had been given, or a regulation was being followed, or the speaker agreed strongly with the necessity.

It is possible for the verb and noun after HAVE TO to change places (…have homework to do). This weakens the idea of necessity, giving more importance to the idea of something merely waiting to be done (see the end of 116. Rarer Uses of HAVE).

The other main use of HAVE TO establishes rather than reports a necessity. The particular kind seems to be exhortation – urging the subject of the verb to behave in a way that the speaker believes to be important. The following sentence could be understood to have this meaning, although it could also be taken to relay an established necessity:

(e) People showing these symptoms have to visit their doctor.

NEED TO and MUST can also exhort (see below), but add extra meaning (danger-avoidance and urgency respectively). Interestingly, if (e) is not reporting and not addressed to anybody, it becomes more wish-like.

A less formal equivalent of HAVE TO in all its uses is HAVE GOT TO. The past tense of HAVE TO is had to. The negative form is a little tricky. If the meaning is “compelled not to”, one can use HAVE TO NOT, but it is rare, the preference being for mustn’t or shouldn’t or a paraphrase like BE NOT ALLOWED TO. Using DO NOT HAVE TO expresses the absence, not the presence of necessity (= “allowed to”).

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3. NEED (TO)

This verb nearly always suggests that the necessity is caused by danger. Its function can be just information-giving, without expecting the addressee to take any action, or action-urging. An example of the first might be:

(f) Salmon need to spawn near river sources.

The danger implied here to be the cause of the necessity is easily recognized, of course, as reproductive failure. Have to could also be used. Although it would be vaguer about the reason for the necessity, this would not greatly affect understanding because the reader’s general knowledge would compensate. Must is possible too. It would suggest some kind of law – natural law perhaps.

The action-urging uses of NEED include exhorting (strongly encouraging), advising and recommending (see 187. Advising and Recommending). The exhortation in sentence (e) above could thus be expressed with NEED as well as HAVE TO. It would probably be a stronger exhortation because of the suggestion of danger.

The past tense form of NEED is needed. The negative is tricky like that of HAVE TO: NEED TO NOT rather than DO NOT NEED TO or NEED NOT, which remove the necessity. For more about to verbs after NEED, see 302. Verbs with a Partner Infinitive, #1. For information about dropping to, see 148. Infinitive Verbs without “to”. For a special use of -ing after NEED, see the end of 83. Adjectives with a “to” Verb. For non-modal uses of NEED, see 208. Verbs with an Object + Infinitive, #2.

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4. MUST (1)

This verb is common for both reporting necessity and creating it. The reporting use normally involves rules, regulations, laws or moral beliefs. Other people’s commands can also be reported. Examples are:

(g) You must have a ticket to travel.

(h) You must be kind to your neighbour.

Spoken by an authority figure, (g) would imply that a legal requirement was being stated, (h) either a moral law or a command from a higher authority. Using must in (f) instead of need would perhaps imply natural law.

The other main use of MUST, creating necessity at the time of speaking, can have different purposes. A common one is to give one’s own strong command (stronger than with BE TO or SHALL). Sometimes this is directly addressed to the people who are expected to obey. Sentence (c) above, replacing are to with must, could have this function, as could (g). At other times the command is often in a formal written document, e.g.:

(i) The claimant must notify the company within three days.

Another non-reporting use of MUST is to highlight particularly important instructions. Instructions differ from commands in being cooperative with their addressees rather than coercive (see 128. Imperative Verbs in Formal Writing). They will mostly use alternatives to MUST, like imperative or ordinary passive verb forms. When  a MUST instruction suddenly appears among these, it is immediately highlighted as being of especial importance.

Thirdly, non-reporting MUST can express very strong exhortation or advice. Sentence (h) could be understood in this way, as could this modification of (e):

(j) People showing these symptoms must visit their doctor.

The past tense form of MUST with all these meanings is had to. The negative uses not.

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5. MUST (2)

This is the logical reasoning use, as in sentences like the following:

(k) x squared is 9 so x must be 3.

The necessity here is the absence of any other possibility. Must be is not compulsory – is is possible too – but using must emphasises the necessity.

An alternative way of writing (k) is with a starting if instead of the so (see 179. Deeper Meanings of “If”, “Likely Conditions”). One might say there is a correspondence between these uses of if and must. The past tense form of must here is again had to. The negative, however, is CANNOT.

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6. SHALL

This verb will not usually express necessity after I or we, and quite often will not after other subjects either. Its main necessity use is the statement of regulations in legal documents, rather like MUST though perhaps with slightly weaker force. It would hence be possible instead of MUST in (i) above.

Sometimes SHALL reports rather than creates regulations, as in this possible public notice:

(l) Bins shall be emptied every Friday.

The use of shall instead of must is perhaps because the regulation, unlike that in (g), does not have to be obeyed by the people being addressed, the public (who do not empty their bins themselves).

The ability of SHALL to express necessity explains why it is incorrect in non-necessity statements like the following, (from 147. Types of Future Meaning), where a decision is being communicated:

(m) Jones will play at right back.

There is no past tense equivalent of necessity-showing SHALL. One might instead say had to or was/were to. The negative uses not.

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7. SHOULD & OUGHT TO

The necessity expressed by these synonymous verbs is usually of a reduced kind, implying that their subject has more choice. As a result, the general usage is advice-giving (see 187. Advising and Recommending). However, the suggestion of choice means that should in particular is also often used in commands and instructions merely as a more polite-sounding alternative to must.

There is no past tense of should or ought to; one must use needed or BE + advisable. Beware of using should have: it suggests that an advisable behaviour failed to happen. The negative uses not.

128. Imperative Verbs in Formal Writing

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The imperative form of English verbs has a wide range of special uses in formal writing

THE NEED TO CONSIDER IMPERATIVE VERBS

Imperative verbs, the simplest of all verb forms in English, may seem an elementary topic in a blog about the more advanced uses of English grammar. There is indeed no need to highlight much about their form, since it is rarely written incorrectly or misunderstood. However, grammar is not just about the construction of forms; it also involves knowing when and when not to use them (see 100. What is a Grammar Error?).

The problem with the use of imperative verbs is that the full range of possibilities is not always appreciated. Many people, if asked, will associate the imperative form more with commanding than anything else, when in fact this is not necessarily its main use at all. Part of the reason for such a reaction may be the misleading nature of the name “imperative”, which, being derived from a word in the Latin language meaning “command”, is strongly suggestive of that idea.

Here is an example of an imperative verb usage that is not for commanding. It is taken from the Guinlist post 33. Complex Example-Giving:

(a) Air pollutants cause many problems. Consider sulphur dioxide.

The main purpose of the underlined imperative here is to signal the start of a multi-sentence example. This post is about the variety of such non-commanding uses that imperative verbs can have in English. First, though, it is as well to be reminded of the various physical features of imperative verbs.

Imperatives are one of three verb form types that grammarians say can be the only verb in an English sentence, the others being the familiar ordinary type (“indicative”) and the “subjunctive” (see 88. Exotic Grammar Structures 1, #6).

Most imperative verbs are just base or “stem” forms without any ending or auxiliaries, e.g. see, describe, take. Other words that can be added include do not (the negative form), do (for emphasis – see 125. Stress & Emphasis), let us/me (to shift the focus from “you” doing something) and let us/me not. The subject of an imperative verb is not usually mentioned, but is mostly understood to be “you” (see 143. Subtleties of “-self” Words).

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FORMAL USES OF IMPERATIVE VERBS

Important formal writing uses of imperative verbs include instructing, cautioning, highlighting, referring, illustrating, hypothesising, advising and signposting.

1. Instructing

Instructions say how to achieve something desirable. They are directions rather than commands because they do not compel – their addressees are assumed to be seeking them (see 314. Words with Complicated Grammar 4, #4).

Academia has numerous well-known uses for instructions. Scientific and technological subjects employ them to specify laboratory procedures, Mathematics spells out steps in calculations with them, and all subjects use them in rubrics for exercises and tests (see 94. Essay Instruction Words). Professional writing too has various uses. Consumers often need instructions for understanding the use of a newly-purchased product. Teachers may base lesson plans on them. Cooks construct recipes with them.

Verbs are central in instructions. They are not always imperative; they can be in the ordinary form instead (either with you or, more formally, in the passive voice – see 46. How to Avoid “I”, “We” and “You”), but the imperative form is common, especially outside academia. It is not inappropriate in any way (see 166. Appropriacy in Professional English), so does not need to be made more polite-sounding with extra words. A particular misjudgement in this respect that I encountered recently was in instructions for a new satnav, where please accompanied every imperative.

Another verb form that instructions sometimes use instead of the imperative is one containing a “modal” verb like should (suggesting advice) or emphatic must. However, these forms are mainly found when other verbs in the same instructions are in the imperative form – it would sound strange to use modal verbs exclusively. Consider this real-life exam question:

(b) Discuss the ethics of the two approaches described above, coming to a reasoned conclusion about which one you would use. You must also discuss the reasoning behind your final choice.

The underlined use of must is acceptable as an instruction because it follows an imperative form discuss at the start. Switching to must might just be for variety (see 24. Good and Bad Repetition), but it could also be emphasising the particular importance of the associated instruction (see 129. Differences between Necessity Verbs).

Note the use of coming in (b). It too is an instructional verb. The -ing ending is just an alternative to and used so as not to have too many short sentences together (see 101. Add-On Participles and 210. Process Descriptions, #4).

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2. Cautioning

This use is often associated with instructions. It differs from them in not giving a new step in a procedure, but rather indicating something to do (or have) or not do (or not have) during a step. Its aim is the prevention of disasters. Undesirable actions are most simply indicated by do not… before an imperative verb or, more forcefully, never or under no circumstances (see 310. Aspects of Negation, #8).

A more positive way of cautioning is with make sure. It normally needs a following that (explicit or “understood”):

(c) Fill the tube with the liquid. Make sure (that) no bubbles are present.

Other useful verbs are ensure, be sure, be (very) careful, take care, mind and see (see 315. Ways of Using SEE, #12). If an unwanted outcome lacks a verb (e.g. the presence of bubbles), a suitable imperative is beware of or (less formally) watch out for.

Should and must can also be used for cautioning. The second sentence in (c) could be rephrased No bubbles should / must be present.

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3. Highlighting

To highlight something is to draw attention to it, thereby suggesting its importance. Imperative verbs that do this include note, notice, observe, keep in mind, bear in mind and remember (= memorise). For the difference between NOTE and NOTICE, see 132. Tricky Word Contrasts 4, #4. The highlighted information may follow any of the listed verbs as an object noun or a that statement, or it may be given in an independent sentence in which the highlighting verb is surrounded by parenthetical commas (see 199. Importance and Unimportance, #4). Consider this:

(d) Instruction verbs can end in -ing.

Highlighting can be achieved with Note that at the start or note between commas after verbs. An informal equivalent of either possibility is the Latin-derived abbreviation NB (see 130. Formal Abbreviations).

Sometimes in statements like (d), how is preferred to that. That suggests the highlighted point is not obvious, how that it is (see 271. Tricky Grammar Contrasts 3, #5).

In addition to the verbs listed above, see has a highlighting role if followed by how: before that it is cautioning instead. Ignore (the fact that) highlights information as unimportant.

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4. Referring

The typical way in which professional documents invite consultation of another information source (either a separate document or a different part of themselves like a previous paragraph or a diagram) is with the source as the subject of an ordinary verb (104. Naming Data Sources with “As”).

Imperative verbs, by contrast, have the information source as their object, making the reader (“you”) their implied subject, so that the invitation sounds more personal. A favourite verb with this use in this blog is see. Alternatives are compare, go to, refer to and remember (= recall), all usable with please. There are also the Latin abbreviations cf. and qv. (see 130. Formal Abbreviations).

The most common position for an imperative referring verb is after the information from the source, helping to give the source name within brackets (see the end of 294. Parentheses). The verb is omissible here, but likely to be present when the source is in the same text but not nearby, e.g. … (see page 6). Omission is more likely if the source is visible or in a different text (see 76. Tenses of Citation Verbs).

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5. Illustrating

The imperative consider in (a) above has this use. It is usually followed by an object noun illustrating a general idea in the sentence before, and then one or more further sentences clarifying the illustration (see 33. Complex Example-Giving). If consider has a following -ing verb (gerund) instead of a noun, it will probably be advising rather than illustrating (Consider visiting your doctor…).

Other imperative verbs that can introduce exemplification include take, imagine, suppose and say. Take is usually a straight alternative to consider (see 264. Variations in the Use of TAKE, #11). Suppose and imagine need an object naming a hypothetical rather than factual idea. After suppose, this object must start with that, but after imagine it can also be an ordinary noun. Say occasionally precedes that too, but more often is an alternative to for example for showing short, simple examples (see 1. Simple Example-Giving).

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6. Hypothesising

An imperative verb can replace if and an ordinary verb in sentences like this:

(e) Break the speed limit and a fine will have to be paid.

Not every use of if can be replaced by an imperative verb. It seems that in most cases the if verb must express an action rather than a state. An example of a state after if is If demand is constant… . For more details, see 88. Exotic Grammar Structures 1, #3.

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7. Advising

As mentioned above, consider + -ing is likely to be understood as advising. Other imperative verbs seem usable for advising if they are accompanied by some further clue that this meaning is intended – otherwise they might sound rather dictatorial. Clues might be contextual or verbal, for example being preceded by my advice is… (see 187. Advising and Recommending).

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8. Signposting

Signposting clarifies the organization of a text by saying how particular points are related to others. Imperatives with let me or let us can achieve this, especially in spoken communication, by indicating that a point is the start of a new topic (see 186. Language in Oral Presentations). A typical example is:

(f) Let us examine the importance of engineers.

The underlined words mean “I will now examine …”. Other verbs usable like this include ANALYSE, CHARACTERISE, CLARIFY, COMPARE, CONSIDER, CONTRAST, DEDUCE, DIFFERENTIATE, ELUCIDATE, ENUMERATE, EXPOSE, IDENTIFY, ILLUSTRATE, INVESTIGATE, LIST, LOOK AT (informal), SPECIFY and RETURN TO.

Imperatives with let are not the only way of introducing a topic. Others are considered within this blog in the posts 122. Signpost Words in Multi-Sentence Lists,  147. Types of Future Meaning,  178. How to Write a Heading,  186. Language in Oral Presentations and 274. Questions with a Hidden Meaning (#8).

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The above uses of imperative verbs seem the most important in formal writing. However, it should be noted that there are plenty of others in the wider English language – for example, welcoming (come in!) and advertising (Get the best prices here). For a little about the latter, see “Stylistic Appropriacy” in 165. Appropriacy in Professional English.