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)

夏季休暇[kakikyuuka] summer vacation
季刊[kikan] quarterly (e.g. magazine)
季語[kigo] seasonal word (in haiku)
季候[kikou] season
季節[kisetsu] season

季節はずれ[kisetsuhazure] unseasonable
季節的[kisetsuteki] seasonal
季節風[kisetsufuu] seasonal winds
四季[shiki] four seasons
冬季[touki] (season of) winter

へし折る[heshioru] to smash
一折り[hitoori] one box
右折[usetsu] turning to the right
右折禁止[usetsukinshi] No Right Turn!
我を折る[gawooru] to concede a point

解折[kaiseki] analysis
回折[kaisetsu] diffraction
回折格子[kaisetsukoushi] (diffraction) grating
曲折[kyokusetsu] windings
九折[kyuusetsu] many turns (in a road)