In English there are no masculine or feminine forms. English uses gender specific nouns for a male or a female.
The word concubine is a gender specific noun for a woman; a word for woman who lives with a man but has lower status than his wife or wives.
There is no equivalent noun to apply to a male except perhaps a slave.
Having a concubine is not considered adultery in some cultures where it is accepted as a form of relationship outside of marriage. However, in many societies and legal systems, having a concubine may be considered a form of infidelity or adultery, depending on the context and cultural norms.
that is the masculine form
Gerald is the masculine form. The feminine form is Geraldine.
Dennis is the masculine form of Denise.
The masculine plural form of malo is malos
Master is the masculine form. Mistress would be the feminine form.
The masculine form for "tendre" in French is "tendre" as well. The word does not change in form based on gender.
The masculine form of "duke" is "duke," and the feminine form is "duchess."
Любымый -- lyubimiy
The masculine form of "trendy" in French is "tendance".
The masculine plural form of "amable" is "amables."
It is spelled Führer, and it is the masculine form of "the leader"