英语语法分析

Menstruation may cease when a woman is anywhere between forty-five and fifty years of age.

月经可能在女性45至50岁之间停止。

《柯林斯英汉双解大词典》

For the first 21 days after menstruation, estrogen hormones create a feeling of well-being and give generally happy feelings.

大多数绝经前的女性在月经之后的21天里，体内的雌激素会产生一种健康幸福感。

Menstruation (a period) is a major stage of puberty in girls; it's one of the many physical signs that a girl is turning into a woman.

月经（例假）的来到是女孩青春期中经历的一个重要阶段；它是女孩变为女人的众多生理变化之一。