their - poss.pron. (attrib.)
1 of or belonging to them or themselves (
their house;
their own
business).
2 (
Their) (in titles) that they are (
Their Majesties).
3 disp. as a third person sing. indefinite meaning 'his or her' (has anyone lost
their purse?).
[ME f. ON their(r)a of them, genit. pl. of sÁ THE, THAT] 
