例句
'Ours' and 'their' are possessives.
ours和their是所有格代词。
《牛津词典》
Possessives are often used in expressions of time.
在时间的表述中，经常用所有格。
When you refer back to indefinite pronouns, you use plural pronouns or possessives, and a plural verb.
但指代不定代词的需用复数代词，物主代词及复数动词。