*kwetwer-
“四”的原始印欧语根。
它构成了以下词语的全部或部分: cadre; cahier; carillon; carrefour; catty-cornered; diatessaron; escadrille; farthing; firkin; fortnight; forty; four; fourteen; fourth; quadrant; quadraphonic; quadratic; quadri-; quadrilateral; quadriliteral; quadrille; quadriplegia; quadrivium; quadroon; quadru-; quadruped; quadruple; quadruplicate; quarantine; quarrel(n.2)“十字弩的方头螺栓”; quarry(n.2)“采石场”; quart; quarter; quarterback; quartermaster; quarters; quartet; quarto; quaternary; quatrain; quattrocento; quire(n.1)“书籍的四折页”; squad; square; tessellated; tetra-; tetracycline; tetrad; tetragrammaton; tetrameter; tetrarch; trapezium。
它是“梵语 catvarah,阿维斯塔语 čathwaro,波斯语 čatvar,希腊语 tessares,拉丁语 quattuor,奥斯克语 petora,古教会斯拉夫语 četyre,立陶宛语 keturi,古爱尔兰语 cethir,威尔士语 pedwar”存在的假设来源/证据。