Girl
Woman, Female
noun
A woman child is just a girl!
女子 is a relatively formal word commonly used in contexts where classification or categorization by gender is used, such as in sports or school settings.
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.
そっちは女子トイレですよ。
The ladies' room is over there.
女子プロレスのチケットをプレゼントした。
I gave a women's professional wrestling ticket as a present.
女子バレーボールのチームキャプテンでした。
I was the captain of the women's volleyball team.