Conjunctions and connectors express similar meanings but follow different rules of grammar and punctuation
MAIN DEFINING FEATURES OF CONJUNCTIONS AND CONNECTORS
Conjunctions and connectors both feature in other parts of this blog, but their importance in professional writing and the confusions that they cause make it useful to compare them more directly.
The main characteristic of both of these word kinds is, of course, that they join or link. However, this is a rather vague idea that needs to be considerably clarified. Prepositions too can be thought of as linking words (see 84. Seven Things to Know About Prepositions). What separates conjunctions and connectors from them is the fact that they introduce statements containing subjects and verbs – prepositions can only introduce nouns by themselves or verbs with -ing.
The difference between conjunctions and connectors is in the kind of link that they make. Consider these examples:
(a) CONJUNCTION: Mount Kilimanjaro is on the Equator, but it has a covering of snow.
(b) CONNECTOR : Mount Kilimanjaro is on the Equator. Nevertheless, it has a covering of snow
In (a), the conjunction but is “joining” in two different ways. Firstly, it physically joins the two verbs is and has into the same sentence – a new verb with no physical link must be in a new sentence (see 30. When to Write a Full Stop). Conjunctions are not the only kinds of words that allow extra verbs into a sentence (others include relative pronouns, participles and question words), but they are an especially frequent type of physical joining device. The second way in which conjunctions join verbs is mentally. In sentence (a) but suggests what follows is surprising after the statement before. Linguists would call physical joining “syntactic” and the mental kind “semantic”.
In sentence (b), on the other hand, the connector does only one kind of joining: the mental/semantic kind (the same mental link as the one shown by but). There is no physical joining in (b): the connector nevertheless is in a new sentence. This is hardly surprising: connectors are very similar to – or even a subtype of – adverbs, most of which are not linking in any way at all (see 121. Sentence-Spanning Adverbs).
Thus, the main similarity between conjunctions and connectors is that they both show a mental link between two statements containing a verb. The main difference is that only conjunctions also create a physical, grammatical link. It is probably this difference that makes some people call connectors “logical connectors”.
A slightly confusing complication is that sometimes we see a conjunction and a connector used together. For example, in (b) above it would be possible to say but nevertheless, with a comma instead of a full stop before. However, the essential difference between conjunctions and connectors remains the same: the conjunction (but) is doing the physical linking (making the comma possible), while the connector is adding its mental meaning to that of the conjunction – making it stronger. In other words, combinations like but nevertheless are emphatic conjunctions. They can only be made with a few conjunction-connector pairs: other examples are in the post 125. Stress and Emphasis.
Knowing these points is, of course, not enough to ensure that connectors and conjunctions are used correctly; one must also know which words make conjunctions and which make connectors. Unfortunately, there is no rule on this: you just have to remember which expressions are which. The meaning is no guide because, as shown above, both types of expression can have the same meaning. There are some opportunities to make the correct choice in the post 138. Test your Command of Grammar.
OTHER DIFFERENCES BETWEEN CONJUNCTIONS AND CONNECTORS
The main other differences concern punctuation and sentence positions. They are:
(i) A conjunction does not usually have a following comma but a connector does (see 50. Right & Wrong Comma Places).
(ii) A conjunction usually comes before the subject of its verb, but a connector quite often comes later. In example (b), nevertheless can be placed after any of the other words in its sentence.
(iii) Most conjunctions may go either before or between the two verbs that they join (see 25. Conjunction Positioning and 64. Double Conjunctions), but connectors must go between them. In example (a) above, but is actually exceptional in that it cannot go before the two verbs, just like a connector. The conjunction although is more typical in its possibilities:
(c) Although chickens have wings, they cannot fly.
(d) Chickens cannot fly although they have wings.
Lists of conjunctions like but (called “coordinating”) and conjunctions like although (called “subordinating”) can be found under 36. Words Left out to Avoid Repetition. See also 37. Subordination: Grammar for Good Repetition.
MEANINGS EXPRESSED BY CONJUNCTIONS AND CONNECTORS
In the above examples, the mental link, or meaning, of the conjunctions and the connector was the same: the surprising nature of the statement made with the second verb. This meaning is one of very many that different conjunctions and connectors express. Some can be read about elsewhere in this blog in the posts 18. Relations between Sentences and 112. Synonyms of Connectors, and a comprehensive list can be found in the book Cambridge Grammar of English. Further examples are as follows:
(e) CONJUNCTION: After evening falls, mosquitoes become active.
(f) CONNECTOR : Evening falls. Then/Afterwards mosquitoes become active.
The mental link here is that the event expressed by the second verb has a later time than the event expressed by the first verb.
(g) CONJUNCTION: If it rains, the visit will be cancelled.
(h) CONNECTOR : It might rain. In that case the visit will be cancelled.
In each of these, the first verb helps to show a hypothetical future event and the second one indicates a consequence of that (see 118. Problems with Conditional “if”).
Two points can be made about the variety of meanings that are possible with conjunctions and connectors. Firstly, most conjunctions seem to have many connectors of similar meaning. Here are some more examples:
Lists of Connectors Corresponding to Individual Conjunctions
additionally, also, as well (not first word), besides this, furthermore, in addition, moreover, too (not first word); afterwards, next, subsequently, then, thereafter; as a result. For more on some of these, see 122. Signpost Words in Multi-Sentence Lists.
all the same, even so, however, nevertheless, nonetheless, still, yet (for a special use of these, see 51. Making Concessions with “May”); by contrast, in contrast, on the other hand; on the contrary (see 20. Problem Connectors).
SO, SO THAT (also BECAUSE/SINCE at the start)
SO (following “JUST AS …)
similarly, likewise, in a similar way, in the same way (see 82. Pitfalls in Making Comparisons)
alternatively, if not, otherwise
BECAUSE/SINCE (between the linked verbs)
this is because, the reason is that
BEFORE (before the linked verbs)
beforehand, before this, first
BEFORE (between the linked verbs)
afterwards, next, subsequently, then, thereafter
meanwhile, at this time, at the same time, at that moment.
The reason why there are many connectors for each conjunction is probably that conjunctions have many different meanings (like most small words – see 3. Multi-Use Words), while connectors tend to have just one. For example, but can express either “contrast” or “concession” (see 20. Problem Connectors, problem #3); and and can express not only addition but also result (see 32. Expressing Consequences).
The second point to be made about the meaning variety of conjunctions and connectors is that overall connectors express more meanings than conjunctions. This is indicated by the existence of connectors with no corresponding conjunction at all, such as for example, for instance, in particular, in fact, indeed, instead, similarly, in short, at least and at last. The first two of these also have a preposition-like use (with a comma before them rather than after), but no conjunction one (see 33. Complex Example-Giving).
For advice on using at last, see 20. Problem Connectors; for advice on similarly, see 149. Saying How Things are Similar. Note also that, despite the variety of connectors, English seems to lack one for one particular inter-sentence meaning: see 117. Saying More Precisely What You Mean.
CHOOSING WHETHER TO USE A CONJUNCTION OR A CONNECTOR
There seem to be a number of considerations in choosing between a conjunction and a connector. The first is to do with whether or not the next words say something already known to the reader. In sentence (e) above, the conjunction after suggests that evening falls is already known to the reader, and the main message is about mosquitoes becoming active; while in (f) the connector afterwards indicates that evening falling is something the reader is being told here because it has not already been mentioned. The ability of conjunctions to introduce already-known ideas seems to belong particularly to the subordinating kind (see 37. Subordination), but only when they are used at the start of the sentence before both of the joined verbs.
The second main consideration in choosing between a conjunction and a connector could be the degree of separateness that we might wish to give to the two joined verbs. Putting them into the same sentence with a conjunction suggests that they are somehow part of the same idea, while putting them into two different sentences suggests that they are two different points (this kind of choice is widespread in writing – see 59. Paragraph Length for an illustration of how the same applies in paragraph design). Compare these examples:
(i) Cars are dangerous and they pollute.
(j) Cars are dangerous. Moreover, they pollute.
Sentence (i) seems to be saying one thing by means of two points, that cars are bad; while (j) appears to be emphasising that there are two separate disadvantages.
A third possible reason for choosing to say something in a new sentence by means of a connector could be the fact that connectors tend to have a more precise meaning than conjunctions. Being precise is especially important in academic and professional writing, and that might explain why connectors are especially common in those fields. An alternative way of making a conjunction meaning more precise is by paraphrasing it with a verb (see 131. Uses of “Action” Nouns).