在英語合成詞中，有一種不是很普遍的，也較少人注意的，那就是疊聲合成詞(repetition compounds)。
疊聲合成詞多數是名詞，也可轉化為形容詞、動詞或副詞，有三種形式：
Ⅰ兩個字都相同，如：
● He pooh-poohed my idea.(輕視)
● It is a hush-hush report not to be made public.(秘密的)
● The boy said bye-bye to his parents.(再見)
其他類似的疊聲合成詞有：
clank-clank(鏈子聲), drip-drip(雨水聲), tap-tap(打字機的聲音), so so(馬馬虎虎), goody-goody(偽善的), fifty-fifty(各半的), pretty-pretty(打扮得很俗氣的), thump-thump(砰然聲), snip-snip(剪聲)等。
Ⅱ第二字的元音和第一字的不同，如：
● Electric networks criss-cross the whole island.(交叉往來)
● The government dilly-dallied over lengthening the retirement age.(猶疑不決)
● The blinds flip-flopped in the wind.(飄搖、搖曳)
● The drunkard zig-zagged along the road.(彎彎曲曲地走)
● Most women like knick-knacks.(小裝飾品)
● Is it possible to get rid of the riff-raff of a society?(下等人)
● The graduating students had a pleasant sing-song in the garden.(歌唱會)
● Do you like wishy-washy soup?(淡而無味的)
Ⅲ第二字的輔音和第一字的不同，如：
● Barbarians in ancient times had to kow-tow to government officials.(叩頭)
● Some people are not used to the hub-bub of the city. (喧囂)
● I pity those who lead a humdrum life year in year out.(單調的)
● Willy-nilly, young people at the age of 18 must go for military training.(不管願意或不願意)
● Don't play hanky-panky with your friends.(陰謀詭計)
● When rain suddenly came, the pedestrians ran helter-skelter.(狼狽地)
● Tom and his friends used to hob-nob in the bar.(共飲、親切地交談)
● The defeated soldiers retreated pell-mell.(混亂地)
● The market in the morning is usually filled with hurly-burly.(喧鬧)
疊聲合成詞形象清新，但數量不多，用的範疇也較局限，通常都不在嚴肅或正式的場合出現。