While the radical meaning of this Latin
word is 'Friend' (fem.
), it was used commonly to describe a certain custom of Ancient Rome
Amica was the title of one kind of a set of official and semi-official concubines in Rome. When a wealthy unmarried Roman citizen (usually a patrician, but not necessarily) took a fancy to a young girl (usually around the age of 13-14) of a poor family of Roman citizens, he could offer her father to make her his Amica. If the girl’s father (and grandfather if he was still alive) agreed, the wealthy man would give the girl’s family a certain amount of money (that was agreed upon in careful negotiations between the man and the girl’s father or grandfather), and would take the girl to live with him. The wealthy man was responsible to the girl’s livelihood (many elderly citizens wanted to boast in their Amicae and pampered them no-end), education and was legally responsible to her (like a husband), and in return the Amica would take care of her man in every respect and supervise over his household. The arrangement could be terminated by the man at any time, but it was considered shameful to send an Amica away to her family without means of support and without her consent (or at least proper notice in advance).
No citizen was allowed to have more than one Amica at any one time, nor could he marry as long as he had an Amica.
It is quite famous that the Emperor Claudius kept an Amica called California before he became Emperor, between his first and second wives.