Use this checklist as a list of reminders while you are editing your paper.
10. Apostrophe Errors
Apostrophes indicate possession for nouns ("Jim's hat," "several years' work") but not for personal pronouns (its, your, their, and whose).
Apostrophes also indicate omissions in contractions ("it's" = "it is").
In general, they are not used to indicate plurals.
In the current conflict its uncertain who's borders their contesting.
In the current conflict it is [it's] uncertain whose borders they are [they're] contesting.
The Aztecs ritual's of renewal increased in frequency over the course of time.
The Aztecs' rituals of renewal increased in frequency over the course of time.
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Still unsure? For more information and examples, check out our grammar and style FAQ.