duad, dual, guan, guar, luau, quad, quag, quai, quay, yuan
Some words that have the letters ME twice in the middle are:amendmentcommencementdismembermentmeantimemeasurementmementomerrimentmesmerisemetronomesometimesummertime
5 letter words that contain FOR:forceforgeforgoformsforum
Words that have "tt" in the middle include "butter," "letter," "batter," and "latter." These words typically contain the double "t" between two other letters, contributing to their pronunciation and meaning.
Boer, does, goes, hoes, noes, poet, roes, toes, woes
Some six letter words with FF in the middle are:wafflebafflebufferduffermufflepifflesufferduffelpuffindiffer
6-letter wordsdewier
Words that have the letter I twice in the middle are skiing and coniine (it's a poison).
Bookkeeper and jackknife are words. They contain the letters kk.
Nerve and nerdy are words. They contain five letters.
Cylin
Some six letter words with OOS in the middle:IgloosKazoosWazoosYahoos
There are no English words that contain all those letters, but here are some eight-letter words: alehouse, hamulose