138. Test Your Command of Grammar



Take a short test to measure and increase command of common grammar difficulties


This post is based on a grammar test that I once composed for an end-of-year university exam – identifying and correcting deliberate grammar errors in a written paragraph. Readers are invited to try the test for themselves, and then read through the answers and their explanations. Most of the errors are also mentioned in other parts of this blog; they are repeated here in order to advertise those other parts or provide useful reminders of their content.

The word “command” in the title above has been preferred to “knowledge”. It covers not just knowledge of grammar rules but also skill in their use. Knowledge alone of foreign language grammar rules is known to be insufficient for avoiding grammar errors from the fact that most people who spend a lot of time and energy acquiring it through memorisation still often make mistakes when they get into real communication.

A paragraph full of grammar errors is not as effective as real communication for testing grammar command, but at least it is better than mere questions about rules. Guidance on recognising grammar errors can be found within this blog in the post 100. What is a Grammar Error?. More common errors are listed on the Common Errors page.



The paragraph below has errors of grammar and punctuation. The latter are included because they are best explained with grammar rules. A corrected version of the paragraph is provided at the end of the post.




The paragraph contains 24 deliberate errors. I was amazed that my computer’s WORD program only underlined one of them in blue as potentially wrong (for more on this problem with computers, see 68. How Computers Get Grammar Wrong 1). Readers who manage to recognise and suitably correct at least 18 of the errors with very few unnecessary changes probably possess a good command of grammar.

1. why is coal

The verb is here needs to follow its subject coal. The reason is that the question is indirect and hence, unlike direct ones, unable to have any part of the verb before the subject. The need for an indirect rather than direct question is a result of it introducing a topic in a formal written text, a situation where English does not normally have direct questions (see 57. Indirect Questions in Formal Writing).


2. electricity source

Add an before these paired nouns. Three rules explain why it is needed: (a) the article before paired nouns is determined by the second of them (source), since the first is merely describing it like an adjective (see 38. Nouns Used Like Adjectives); (b) if the second noun is singular and countable (as source is), it must have either a(n) or the (see 110. Nouns without “the” or “a”); and (c) a(n) is the right choice if the meaning of the whole phrase is “generic” – lacking reference to a particular time (see 89. Using “the” with General Meaning).


3. is easily

Change the adverb easily into the adjective easy. Only adjectives and nouns can stand alone after it is when the it indicates a later verb (see 103. Postponed Subjects in “It” Sentences). Manner adverbs like easily are only possible alongside an adjective or noun (e.g. is easily the best). For more about adverbs, see 120. Six Things to Know about Adverbs.


4. several … advantage

Add plural-showing -s to the countable noun advantage: the vague number word several can only accompany countable plural nouns.


5. it’s cheapness

Remove the apostrophe. The required meaning is “of it”, but it’s means “it is”. This is an extremely common error even among speakers whose mother tongue is English.

The probable reason why the apostrophe is so often incorrectly added is that a common meaning of apostrophes – that of possession (see 58. Optional Apostrophe Endings) – is being expressed. The reason why no apostrophe is possible is that its is an adjective, not a noun; only nouns can have apostrophes. Other adjectives that carry the meaning of possession are my, his, her, their, your and our.


6. it is readily available

Change to its ready availability – a noun phrase instead of a subject-verb statement. The reason is that it is linked by and to a preceding noun phrase (its cheapness), the rule being that expressions linked by and must all have the same grammatical form as the first (see 93. Good and Bad Lists).

Note how changing the adjective available into the noun availability also requires readily, an adverb, to become the adjective ready. This is because adverbs describe verbs or adjectives but not nouns (see 120. Six Things to Know about Adverbs).


7. etc.

This abbreviation is the correct one for suggesting an unfinished list (see 130. Formal Abbreviations), but it should not be used here because its meaning has already been expressed by such as. Having the two together is an example of unnecessary repetition (see 1. Simple Example-Giving and 24. Good and Bad Repetition). The correction is to delete etc. and insert and after cheapness.


8. however

This should start a new sentence and have a comma after it. The reason is the following verb is, which cannot be in the same sentence as the previous one (also is) because new verbs need new sentences, unless they have a joining device (see 30. When to Write a Full Stop). However looks like a joining device but is not; it is a “connector” instead (see 40. Conjunctions versus Connectors).


9. to recommend

Change to of recommending. Although possible can be followed by a to verb, possibility cannot (see 78. Infinitive versus Preposition after Nouns).


10. is that,

Remove the comma. The conjunction that cannot be followed by one except in special circumstances (see 50. Right and Wrong Comma Places).


11. produce

Change to singular produces so as to agree with the singular subject coal (see 12. Singular and Plural Verb Choices).


12. to heat

Delete to. A verb after MAKE has no to except when MAKE is passive (see 10. Words with Unexpected Grammar 1 and 141. Ways of Using MAKE).


13. in addition

This is a connector like however (see 7 above), and should be corrected in the same way.


14. so difficult

Change so to very. It is normally used only when the writer expects the strength of the adjective to be already familiar to the reader (see 156. Mentioning What the Reader Knows Already). Here, the writer does not have this expectation and is communicating the strength of the difficulty.


15. because of

Remove of: it is possible only when the reason after it is expressed purely by a noun or noun equivalent (see 72. Causal Prepositions and 61. “Since” versus “Because”). Here the wording of the reason is a statement with a verb (is), necessitating the conjunction because.

An alternative correction is to keep of and reword the reason as a noun equivalent (because of its great bulk). However, this would necessitate similar rewording of the two other reasons in the list. Removing of is easier.


16. is very bulky

Add it before is. Verbs need a subject after an English conjunction, except when the conjunction is of the “coordinating” kind (see 174. Eight Things to KLnow about Conjunctions). The conjunction present here (because) is not of this kind.


17. harm

Change to singular harms so as to agree with the singular subject it (see 12. Singular and Plural Verb Choices).


18. the workers,

Remove the comma. It precedes a relative pronoun (who) that helps to define which workers are meant. So-called “defining” relative pronouns cannot have a preceding comma (see 34. Relative Pronouns and Commas). Normally there would be no later comma either (after extracting it), but another reason for a comma – being just before and – exists here.


19. extracting

Change to extract. Any verb linking with which needs an ordinary tense form, here either are extracting (present continuous) or extract (present simple). To understand why, see 52.Participles Placed Just after their Noun and 133. Confusions of Similar Structures 1. Extracting is not an ordinary tense form, but a participle or gerund.

It is better to have extract than are extracting because the reference is to all times, not a particular one.


20. limited

Add it is just before. As in 19, there is a need for an ordinary tense form (again present simple), this time in the passive voice. Limited by itself with passive meaning is a participle rather than an ordinary tense form..


21. the electricity’s generation

Remove the. It cannot go with either of the following nouns because they are both uncountable with generic meaning. Such nouns normally take the “zero” article” (see 110. Nouns without “the” or “a”).


22. electricity’s generation

The problem is ’s. Although it is often possible on the first of two paired nouns (see 58. Optional Apostrophe Endings), it is not here. The reason is the particular kind of noun pair: the second noun expressing an action of which the first is the object. In such cases, ’s is likely if the first noun has specific reference (meaning particular electricity at a particular time), and not likely otherwise (for electricity in general).  The meaning here is electricity in general.

One correction is simply to remove -‘s (see 136. Types of Description by Nouns (#7). An alternative is to use of (the generation of electricity – see 31. Prepositions after “Action” Nouns 1 and 160. Uses of “of”, #1).


23. the others

Remove -s. Other here is an adjective (it “describes” the following noun energy source). Adjectives cannot have -s. Other can only have -s when it is not an adjective – when there is no following noun. In such cases it is a pronoun, and with plural meaning needs -s (see 133.Confusions of Similar Structures 1).


24. source

Add -s. To avoid this very common error, it may help to remember that a noun after one of must be plural. The reason is that the singular noun implied by one is not the one after of, but an unmentioned one just before of. The whole phrase means “one (source) of the sources”. The first of the two nouns is not mentioned because it would be repetitive (see 36. Words Left out to Avoid Repetition). For more explanation, see 165. Confusions of Similar Structures 2, #6.



If the above paragraph is corrected in the ways suggested above, it would read as follows. Alternative corrections may sometimes be possible.


In considering why coal is still used as an electricity source, it is easy to recognise several major advantages, such as its cheapness and its ready availability. However, there is no possibility of recommending it. The most important reason is that coal produces harmful gases, especially carbon dioxide, that make the earth’s atmosphere heat up. In addition, it is very difficult to transport because it is very bulky, it harms the workers who extract it, and it is limited in supply. There would be much more benefit if electricity generation used one of the other energy sources, such as the sun.


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