As yet no formal marriage bans have been proclaimed.

But without formal marriage," he pointed out, "the alliance between your two groups has no basis.

It was widely known that she had a 27-year-long personal life with Spencer Tracy, outside of a formal marriage.

Monogamy, the predecessor of formal marriage, may have evolved as recently as 20,000 years ago.

To this the king agreed, and made formal marriage between Gul and me.

"A formal marriage only, in your Temple, with only your household as witnesses."

The number of adults with open relationships - be they formal marriages or more informal arrangements - is small.

In ancient days, negotiation between the boy's family and that of the girl preceded the formal marriage.

The Khans loved these people enough to make formal, public marriages with them, and to raise children with them.

Humans also differ by having formal marriages which in many cultures involve negotiation and arrangement between elder relatives.