まっ四角[masshikaku] square
一天四海[ittenshikai] the world
下四半期[shimoshihanki] last quarter (of the year)
弦楽四重奏曲[gengakushijuusoukyoku] string quartet
再三再四[saisansaishi] repeatedly

三寒四温[sankanshion] alternation of three cold and four warm days
四つ[yottsu] four
四つんばい[yotsunbai] (crawl) on all fours
四つ角[yotsukado] four corners
四つ足[yotsuashi] four-footed (animal)

オムツ気触れ[omutsukabure] diaper rash
お気の毒[okinodoku] pitiful
御天気[otenki] weather
利かん気[kikanki] daring
さり気ない[sarigenai] nonchalant

哀れ気[awarege] sad
悪気[warugi] ill will
圧搾空気[assakukuuki] compressed air
圧縮空気[asshukukuuki] compressed air
圧電気[atsudenki] piezoelectricity