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)

愛書[aisho] great love of books
愛読書[aidokusho] favourite book
悪書[akusho] harmful book
案内書[annaisho] guidebook
移動図書館[idoutoshokan] mobile library

遺言書[yuigonsho] testament
遺書[isho] note left by dead person
医書[isho] medical book
一つ書き[hitotsugaki] an item
一書[issho] one letter