The Avestan word θritiia-
Word θritiia-
Meaning third
See also Homeric Greek: τρίτος ‘third’
Linear B: ti-ri-to ‘third’
Tocharian B: trite ‘third’
Proto-Indo-European: *triyós ‘third’
Tocharian A: trit ‘third’

Other words that might be of interest
aēuua ‘one’, ašta ‘eight, 8’, xšuuaš ‘six, 6’, paoiriia- ‘first’, paṇca ‘five, 5’, bitiia- ‘second’, hapta ‘seven, 7’, caθβarasca ‘four’