"Sexual intercourse" may be called "coitus", "copulation", "coition", or "intercourse". "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. This is often called "vaginal intercourse" or "vaginal sex." "Vaginal sex," and less often "vaginal intercourse", may also denote any vaginal sexual activity, particularly if penetrative, including sexual activity between lesbian couples. "Copulation", by contrast, more often denotes the mating process, especially for non-human animals; it can mean a variety of sexual activities between opposite-sex or same-sex pairings, but generally means the sexually reproductive act of transferring sperm from a male to a female or sexual procreation between a man and a woman.