Many words have prefixes that indicate numbers.

for example:

quadruped = an animal with four legs

biplane = an aeroplane with two sets of wings

These prefixes often come from Latin or Greek and include the following:

mono = one

bi = two

tri = three

quart / quad = four

quin = five

sex / hex = six

sept / hept = seven

oct = eight

non = nine

dec = ten

cent = one hundred

mille = one thousand

Knowing the meaning of parts of a word can be helpful with spellings.