Sexual Relationships 
Sexual Health 
When it comes to defining sex, many people, too many people, have varied definitions of sex. Sure, you may say that sex is personal and subjective, but if you want to pull meaningful information and analyze it, then you need a standard definition of it. It is also important when you want to inquire about someone's sexual history so that you can send the data to the epidemiologist; as well as inquire about the sexual history of your significant other. Beware, though, that some people lie, which is not surprising given the taboo nature of the discussion and the social stigma attached to STDs.
What is sex?
Sex typically refers to the situation where the penis or some kind of object is inserted into the mouth, vagina, or anus; or when any part of a person's sex organs is erotically stimulated by a partner or by self with or without penetration. Sex involves erotic stimulation, touching, and pleasure. It is sensual pleasure, or pleasure of the senses (sight, hearing, smell, taste, and touch). Kissing, hugging, spooning, snuggling, playing with breasts or other body parts with erogenous zones may be part of sexual acts, but they normally are not considered sex acts. The definition of sex must be neutrally worded, so that people would be more willing to admit to sexual acts, as well as understand what sex is and how to articulate past sexual experiences verbally.
Now that sex has been defined here, the next step is to get people to use it to standardize the definition of sex. A standard definition may help distinguish the true virgins from the false virgins, which may give better estimates for the number of virgins out of the total population. That way, some people won't use virginity as some sort of status symbol to describe themselves when they really are not. Deception does no one good. A sexually active person who lies about being sexually active may be susceptible to STDs. A true virgin may not receive the admiration she deserves. (Though, to be honest, a virgin usually achieves deep admiration when she does a great deed, like sacrificing her life and becoming a martyr for some kind of noble cause. The traditional term for the male equivalent of virgin is a celibate man, as a non-celibate man implies that he is married and presumptively consummates his marriage by sexual intercourse.) And any celibate person, or any innocent person really, who has sacrificed himself/herself in the face of cruelty and corruption deserves admiration and recognition for the good works.
Another reason why we need to standardize the definition of sex is to promote equality between heterosexual couples and homosexual couples. As far as I know, heterosexual couples do not regard oral intercourse as sex, while gay and lesbian couples do. By having a more generic, inclusive definition of sex, homosexual couples may feel less marginalized by mainstream society. The inclusive definition of sex also considers masturbation as a sexual activity, regardless of whether it's done with a partner or solo. So, a person who has never had partnered sex, but has achieved orgasm through solo sex (masturbation), has had sex before, but that kind of sex is the safest form of sex as there are no pathogens transmitted or unwanted pregnancies, provided that the pathogen mainly spreads by partnered sexual contact and that the person cannot self-fertilize.
Therefore, we need to standardize the definition of sex for greater understanding and communication, as well as for creating a more inclusive atmosphere for homosexual couples and unpartnered singles who have satisfying sex lives, derived from non-traditional means to "have sex".
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