concubines is a form of:

Concubine



noun
1.
(a secondary wife in countries where polygamy is customary, a woman who cohabits with a man although not legally married to him) ស្រីស្នំ, ប្រពន្ធចុង, ស្ដ្រីដែលយកគ្នាមិនបានរៀបការ, អនីតិសង្វាសី-សិនី, សាហាយ
ENGLISH MEANING
noun
1.
A woman who cohabits with a man without being his wife; a paramour.
2.
A wife of inferior condition; a lawful wife, but not united to the man by the usual ceremonies, and of inferior condition. Such were Hagar and Keturah, the concubines of Abraham; and such concubines were allowed by the Roman laws. Their children were not heirs of their father.