- An example of their is a sister of two siblings.
- An example of their is a book written by two authors.
Origin of theirMiddle English theyr ; from Old Norse theirra, genitive plural of the demonstrative pronoun replacing Middle English here, Old English hira: see they
adjectiveThe possessive form of they.
- Used as a modifier before a noun: their accomplishments; their home town.
- Usage Problem His, her, or its: “It is fatal for anyone who writes to think of their sex” (Virginia Woolf). See Usage Notes at he1, they.
Origin of theirMiddle English, from Old Norse theira, theirs; see to- in Indo-European roots.
- (possessive) Belonging to, from, of, or relating to, them.
- they will meet tomorrow at their convenience; this is probably their cat
- (possessive) Belonging to someone of unspecified gender.
- For notes on the usage referring to a person of unspecified gender, see the usage notes for they.
- It is important to distinguish “their" from “there" and “they're". “Their" signifies ownership. “There" designates a place (compare here). “They're" means “they are".
- It should also be noted that this is an exception of the "I before E, except after C" rule, as the combination of "ei" in the middle of the word is not after a "c".
From Middle English, form Old Norse.