The answer to a question that begins "how many?" has to be a number. The number that answers this question will be very large because all the most common letters of English are in that series of letters. In fact, all the letters of the alphabet are there except these:
b j k p q v w x z
So the number is going to be very high, probably in the tens of thousands.
Words that can be made from the letter is 'with' are:hihitIitwit
133 words
Words I can make with the letter is the word 'terror' are:errerrorororeretroroerotrotetotoetore
34 words (not including single letter words)
Words that can be made from the letter in meal are:aalealmamlamlamemaleme
abbeabedacedbabebadebeadbeefcafecaffcecacededacedeaddeafdeedfacefadefafffeeddecade
Three letter words that can be made with the letters 'bingo' are:bigbinboggingobionnibobi
--- 29 words ---7 Letter wordspenguin5 Letter Wordsennuiequippennipiqueunpenunpin4 Letter Wordsninepeinpinequinquip3 Letter Wordsinnnipnunpenpiepinpiupun2 Letter Wordseninnenupepiqiun
kitchen
20
dry
--- 58 words ---7 Letter Wordsharvast6 Letter Wordsarhats5 Letter Wordsarhatavasthaarshartstahrstrashvaras4 Letter Wordsaahsartshaarharthasthatsrashrathratsshatstartahrtarstavstsarvaravarsvasavastvats3 Letter Wordsaahaasahaahsarsartashavahashatrahrasratsatshatartastavvarvasvat2 Letter Wordsaaaharasathashta