ぴかぴか光る[pikapikahikaru] to sparkle
旭光[kyokkou] rays of the rising sun
威光[ikou] power
稲光[inabikari] (flash of) lightning
曳光弾[eikoudan] tracer bullet

栄光[eikou] glory
円光[enkou] halo
炎光[enkou] flame
黄道光[koudoukou] zodiacal light
可視光線[kashikousen] visible ray

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)