(of those things) olia.
(when necessary to indicate gender) ilia; (feminine) elia (pl. forms: lii, ilii, elii, olii, rarely used);
(reflex pronoun) sua (pl. sui).
they and their friends - li e lia amiki.
theirs - lia.
this house is theirs - ca domo esas lia, co esas lia domo.