One very long word that starts with m is: microcryptocrystalline (22 letters)
The longest word that starts with the letter "m" is "methionylglutaminylarginyltyrosylglutamylserylleucylphenylalanylalanylglutaminylleucyllysylglutamylarginyllysylglutamylglycylalanylphenylalanylvalylprolylphenylalanylvalylthreonylleucylglycylaspartylprolylglycylisoleucylglutamylglutaminylserylleucyllysylprolylalanylphenylalanylprolylleucylglutaminylserylthreonylalanylglutaminylleucylprolylleucyllysylmethionylleucylalanylalanylisoleucylglutamylglutaminylserylleucyllysylalanylthreonylalanylprolylprolylleucylglutaminylserylthreonylalanylglutaminylalanylthreonylleucylprolylleucylglutaminylglycylphenylalanylglycylvalylprolylphenylalanylvalylthreonylprolylalanylglutaminylcysteinylphenylalany...". This word is the chemical name for the protein known as titin, which is the largest known protein. It contains 189,819 letters in total.
This is the longest word in the whole world. It has 189,819 letters on it.
methionylglutaminylarginyltyrosylglutamylseryllleucylpheny
A four letter word that starts with J and ends with M: jism.
A seven (7) letter word that starts with M and ends with O: memento
Mussel
mess
methionylglutaminylarginyltyrosylglutamylseryllleucylpheny
Make is a word that means to create and starts with "m".
A four letter word that starts with J and ends with M: jism.
A muscle is a 7 letter word that starts with m and helps you run fast.
A seven (7) letter word that starts with M and ends with O: memento
mademalemanemaskmakemashmathmartmarkmessmeltmeekmeanmealmaremintminemindmilemistmastminkmitemaltmatemoatmissmoonmoodmashmostmolemoltmoremeremeatmeetmustmuskmusemythmothmushmuchmovemoanmademiremacemainmane
MeatMateMakeMindMineMintMoodMeekMaleMailMassmast
mulch
mend
measurement
morons.
magmamajormakermangomangymanormarrymaybemauvemeantmetermessymeritmerrymilkymightminormintyminusmirthmistymitermincemoistmoldymonthmoneymoodymousemoosemotormountmountmouthmossymottomoviemuddymurkymuskymustymutedmazed