Academic Writing for International Students of Science - Jane Bottomley 2015

A3.1 Common punctuation problems
3 Common areas of difficulty in grammar and punctuation

A3.1.1 Apostrophes

The apostrophe denotes possession. Be careful to distinguish between singular and plural nouns:

✵ The bridge’s structure was examined. (one bridge)

✵ The bridges’ structures were examined. (several bridges)

A3.1.2 it’s versus its

it’s is the contracted form of it is/has:

✵ It’s important to note the temperature.

✵ Note the colour of the liquid when it’s cooled.

its is a possessive pronoun like my or his:

✵ When the liquid is heated, its colour changes.

If you avoid contractions, you shouldn’t need to use the apostrophe at all in this case.

A3.1.3 Hyphens in compound adjectives

Compound adjectives are usually hyphenated when they come before a noun, but not when they come after:

✵ an out-of-date technology

✵ a technology which is out of date

✵ a chemically-induced coma

✵ a coma that has been chemically induced

A3.1.4 Brackets

Brackets should be used sparingly as they can interrupt the flow of a text. If you do use them, be careful with punctuation. If the bracketed information is part of the sentence, it requires no specific punctuation, e.g.

✵ The data (collected over six months) revealed a noticeable decline in quality.

If the brackets contain a separate sentence, it should be punctuated as such:

✵ The data revealed a noticeable decline in quality. (All the data was collected over a six-month period.)