Area
noun
The surface that accumulates into one area is a particular area. This has to do with math. When you add all the surfaces together by accumulating them into one calculation, you get yourself the area!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
彼のおでこの面積は100平方メートルある。
The area of his forehead is 100 square meters.