The Proto-Indo-European word *tréyes
Word *tréyes
Meaning three
See also Proto-Indo-European: *tris ‘thrice’
Proto-Indo-European: *triyós ‘third’
Tocharian A: tre ‘three’
Synonyms *trei-, *tréies (m), trisóres (f), treih₂ (n) tri- [prefix]

Comments
Mallory J.P. and Adams D. (2006)

Other words that might be of interest
*hₓok̂tṓ(u) ‘eight’, *dwoi- ‘group of two, two’, *h₁oinos ‘one’, *kʷetwóres (m), kʷetwesóres (f), kʷetwōr (n) ‘four’, *(h₁)néwn̥ ‘nine’, *pénkʷe ‘five’, *sem- ‘one’, *septḿ̥ ‘seven’, *septm̥-k̂ómt-h₂ ‘seventy’, *kswek̂s ‘six’, *dwéh₃(u) ‘two’, *h₁newh₁m̥(h₁néwh₁n̥?) ‘nine’, *tóti ‘so much, many’, *trī-k̂omt(hₐ) ‘thirty’, *kswek̂s-k̂omt(hₐ) ‘sixty’, *kʷetwóres ‘four’, *per(hₓ)- ‘first’, *dwiyos~dwitos ‘second’, *h₁newh₁m̥m/n̥-mos ‘ninth’, *hₓok̂towós ‘eighth’, *kswek̂sos ‘sixth’, *kʷturyós~kʷetwortos ‘fourth’, *pn̥kʷtós ‘fifth’, *septm̥-mós ‘seventh’