their(употр. атрибутивно; ср. theirs); theirs(this book is theirs – это их книга; theirs is a good house – их дом хорош); them(people, animals, things etc. already spoken about, being pointed out etc. • Let's invite them to dinner; What will you do with them); of them; these(The limitations of classical selenodesy... are discussed and methods for overcoming these are described. I. Havkin)
theirs(this book is theirs – это их книга; a person, thing etc. belonging to them • The child is theirs; a friend of theirs (= one of their friends)); their(чей? • This is their flower.Shabe); theirs(чей? • The/This flower is theirs.Shabe); its(говоря о предметах неодушевлённых, животных, когда их пол неизвестен, и иногда о детях)