Refers to the quality or state of being feminine; often used in discussions of gender, psychology, or sociology.
彼女は女性性を大切にしている。
She values her femininity.
この研究は女性性の社会的な側面を探っている。
This research explores the social aspects of femininity.
Compound of 女性 (woman, female) and 性 (nature, quality). The exact historical derivation is uncertain, but the word follows a common pattern for abstract nouns describing qualities.