Vaginal sex or vaginal intercourse is sex involving the vagina. The term is especially used in regard to the insertion of the erect penis into the vagina, known also as "regular" sex or intercourse, after which both people move to create pleasure and possibly orgasm.
In many cultures, legal limitations are imposed upon vaginal sex, for instance specifying it is only permissible within marriage or after a certain age.
If a man ejaculates ("cums") during vaginal sex, he can cause pregnancy unless an effective form of birth control is used. A person can also get sexually transmitted diseases (STDs) this way if their partner has a disease. A condom can prevent both pregnancy and transmission of a STD.
A woman's first vaginal intercourse can be painful but with a capable and attentive partner and the right build-up this need not be the case, though aspects such as age do have a part. Women can prepare for their first intercourse by slowly stretching the hymen open during masturbation or having her partner gently do this for her.