分母 is read as ぶんぼ (bumbo) and means denominator.
ぶんぼ
bumbo
ぶんぼし
denominator and numerator
どうぶんぼ
common denominator
こうぶんぼ
ぶんぼをはらう
to cancel a denominator
さいしょうこうぶんぼ
lowest common denominator
ぼぶんさん
population variance
わかる
I know!
ぶんや
field
わける
to push one's way through (a crowd)
ぶんし
molecule
わかれる
to disperse
ぶんぎょう
division of labor