Chemistry

03. Commas and run-on sentences

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Commas area very necessary form of punctuation. Using them wrongly has three damaging consequences:

A run-on sentence might look like this:

If you read the sentence out loud, you'll feel that it runs on well beyond a length that's comfortable to read. Here are two ways to divide it, changing the text slightly for ease of reading:

A tip: read your text aloud and listen to the flow. If a comma trips you up, it's in the wrong place. If you find yourself puzzled by the sense of your sentence, you may need to replace some commas with full stops. Remember that you're trying to convey information as clearly as possible. Wrongly placed commas do not clarify, they muddle.

In addition to that all-important tip, here are some basic uses for commas:

1. To separate items in a list:

N.B. If the list is long and complicated, it's sometimes also helpful to put a comma before the last item. This is known as a serial comma.

2. To join two related sentences the second of which begins with and, or, but, yet or while, if this makes the text easier to understand:

3. To enclose a subordinate clause (a clause within a sentence that adds information):

4. To provide a small pause after an adverb (e.g. first, secondly, thirdly, however, therefore, furthermore, finally, similarly, subsequently) or adverb phrase (e.g. in the meantime, more importantly, in particular, in conclusion) if the adverb or adverb phrase comes at the beginning of a sentence.
5. To separate out adverbs within sentences, if this makes the text easier to read.
TaskTask TypeDifficulty
Task 1Multiple choiceEasier
Task 2Free textModerate
Task 3Free textEasier
Task 4Free textModerate
Task 5Free textEasier
Task 6Free textModerate
Task 7Free textModerate
Task 8Free textModerate