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.