Courtship, properly understood, is the process whereby both the male and the female are brought into that state of sexual tumescence which is a more or less necessary condition for sexual intercourse. The play of courtship cannot, therefore, be considered to be definitely brought to an end by the ceremony of marriage; it may more properly be regarded as the natural preliminary to every act of coitus.
Havelock Ellis (2015). “Studies in the Psychology of Sex v3: Human Sexuality”, p.198, 谷月社