How to Spell their
their
their - adjective
- Of or relating to them or themselves especially as possessors, agents, or objects of an action
Source: Merriam-Webster Dictionary API
"their furniture"
Etymology
Middle English, from {it}their{/it}, pronoun, from Old Norse {it}theirra{/it}, genitive plural demonstrative & personal pronoun; akin to Old English {it}thæt{/it} that