Coitus is derived from the Latin word coitio or coire, meaning "a coming together or joining together" or "to go together", and is known under different ancient Latin names for a variety of sexual activities, but usually denotes penile—vaginal penetration. Lerner and Laurence Steinberg state that researchers also "rarely disclose" how they conceptualize sex "or even whether they resolved potential discrepancies" in conceptualizations of sex. While most consider penile—vaginal intercourse to be sex, whether anal or oral intercourse are considered sex is more debatable, with oral sex ranking lowest. In this way, they stimulate themselves and each other, often continuing until orgasm in either or both partners is achieved. It is sometimes performed to the exclusion of all other forms of sexual activity, and may include the ingestion or absorption of semen during fellatio or vaginal fluids during cunnilingus.