Monosociality (adj monosocial) in sociology describes social relations (or preference for such relations) with only one sex, of a (putatively) nonsexual nature. The opposite would be bisociality. Monosociality does not imply monosexuality.
A preference for social relations with the same sex is most common in humans, and referred to as homosociality. Heterosociality refers to a preference for social relations with the opposite sex. A group larger than two cannot be satisfied with all present individuals if all members are heterosocial, which may explain part of the dominance of homosociality in social group dynamics.