Gender, Nature, Sex
noun
The kanji and the word are exactly the same. That means they share meanings as well.
せい
This has the same reading as the kanji you learned, meaning you know the reading!
性のところ、女性に丸しておいたよ！
In the gender section, I circled female!
この本は、性教育のための本です。
This book is for sex education.
体の性差は、性ホルモンの働きによって作り上げられているのです。
The physical differences between sexes are created by the action of sex hormones.