出典:Wiktionary
出典:『Wiktionary』 (2026/05/09 22:04 UTC 版)
From Proto-Italic *kʷetru-, from Proto-Indo-European *kʷetwr̥-, with *-twr̥- developing into -dr-; compare the full form quattuor, ultimately from *kʷetwóres. Analogous to Ancient Greek τετρα- (tetra-) vs. τέσσαρες (téssares, “four”).