1.sex的基本意思是“性别,性”,指人的男性或女性,动物的雄性或雌性,用作不可数名词。
2.sex也可表示“性行为,性吸引,性感”,用作不可数名词。
3.sex还可表示“男性或女性”,用作可数名词。
4.the sex可统指“女子们”, the sexes, both sexes, two sexes可统指“男人们和女人们,男女”。
5.the weaker sex作“妇女”解,用于贬义,含有性别歧视的意味。

the weaker sex
女性 woman in general
He always liked to please the weaker sex, but they generally laughed at him.他总想取悦女性,可是她们通常取笑他。
That shop caters exclusively to the weaker sex.那家商店专供妇女需要的商品。

What sex is this fish?这条鱼是雌的还是雄的?
Everyone is welcome, regardless of age or sex.欢迎大家,无论男女老少一律欢迎。
In the space marked “sex”, put an “M” for male or an “F” for female.在标明性别的空白处填上M表示男性,填上F表示女性。
Best grammar schools are single sex.大部分文法学校都是男女分开的学校。
They often had sex together.他们常发生性关系。
Do you think sex outside marriage is always wrong?你认为婚外性关系总是错误的吗?
The couple went for therapy because they hadn't had sex for years.这对夫妇去接受治疗,因为他们多年没有过性生活了。
There's a lot of sex and violence in this film.这部影片中有不少渲染性行为和暴力的镜头。
He never associated with the sex.他从不和女性交往。
Employing just one woman among fifty men is only token recognition of equal rights for the sexes.50个工人中雇用了1个女工只不过象征性地承认了男女平等。
He often talked about the equality between the sexes.他常常谈论男女平等的问题。
There has always been some conflict between two sexes.两性之间从来就有矛盾。

sex也可用作动词,表示“区别…的性别”。例如:
His job is sexing day-old chicken.他的工作是鉴别出生一天的小鸡的雌雄。

［派生词］ sexism n.(尤指对女性的)性别歧视,性别偏见‖sexy adj.性感的,有性的吸引力的
［词源］  ＜拉丁语sexus＜古法语sexe(性别)