How many syllables can a foot have?

Feet, in poetry, are the patterns of stress in the syllables used.

For example, a foot can be:-

an iamb, which is a short syllable followed by a long one (de-dum), or

a trochee, which is a long syllable followed by a short one (dum-de), or

an amphibrach, which is a long syllable between two short ones ((de-dum-de), or a number of other combinations that each have their own names.