Why is it feet and not foots?

The same reason it's geese for goose, lice for louse, mice for mouse, etc... It has something to do with an old English rule called I-mutation. It is the raising and fronting of a root vowel in anticipation of "i" or "y" sound in a suffix. read more

Foot and feet are used rather often and words that are used more often usually resist change more than words that are rarely used, and"foot/feet" was also a unit of measurement, and thus even more resistant to change. read more

Yes, and when you walk on foot there is a grammar rule that says it's not"on feet". Grammar rules are not something passed onto us by some high committee. Grammar"rules" are really just descriptions of what we already do anyway, long before we go to school to learn that grammar even exists. read more