The Proto-Indo-European word *tréies (m), trisóres (f), treih₂ (n) tri- [prefix]
Word *tréies (m), trisóres (f), treih₂ (n) tri- [prefix]
Meaning three
See also Linear B: ti-ri-po-de ‘tripod’
Linear B: ti-ri ‘three’
Lycian: trei ‘three’
Latin: trēs ‘three’
Tocharian B: trey ‘three’
Homeric Greek: τρεῖς ‘three’
Homeric Greek: τρία ‘three’
Proto-Anatolian: *téri- ‘three’
Synonyms *trei-, *tréyes

Comments
Arm. erek'/yerek'/yerek', Alb. tre/tre, Lith. trys, Ltv. trīs, Gaul. treis, Gm. drī/drei, Eng. þrēo/three, Gk. treis, Hitt. tri-, Av. θri, Illyr. tri-, Ir. treí/trí, Kashmiri tre, Lyc. trei, Kamviri tre, Oscan trís, ON þrír, Old Prussian tri, Osset. ærtæ/ærtæ, Pers. çi/se, OCS trĭje, Polish trzy, Russ. tri, Skr. tri, Toch. tre/trai, Lat. trēs, Umbrian trif, Goth. þreis, Welsh tri, Phryg. thri-

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’, *triyós ‘third’