Marriage is an institution and it has three basic parts.
History – God ordained marriage as an institution for men and women when He created men and women.
Requirements – Marriage requires the sexual union of one man and one woman.
Boundaries – The union between a man and a woman is not to be broken except by the death of either the husband or wife.
Any other requirement or boundary is not marriage but a pathology of marriage, a deviation from the institution. Multiple sex partners, either through casual sex or marriage, divorce, and remarriage, is not marriage. Two men or two women is not marriage. Casual sex without lifelong fidelity is not marriage. These things violate the institution and its fixed requirements.
The concept of “traditional marriage” is misleading because it assumes the reality of “alternative marriage” where there is only marriage. The King James bible uses the term “fornication” to describe all heterosexual sex that is not within the institution. Sodomy is the term used to describe two men or women attempting to have sex, since biologically they cannot have sex.
Sex and marriage are considered one and the same. A man or woman who has had more than one sex partner has committed adultery and violated the institution of marriage. The only allowance is one spouse being sexually faithless, which grants an exception of mercy.
Talk of marriage equality is merely language meant to mask the desire for liberation from the institution of marriage for a life of casual and free sex, which is not marriage.