Cohabitation

n. living together as husband and wife; condition of sharing the same living space

Cohabitation is an emotional and physical intimate relationship which includes a common living place and which exists without legal or religious sanction.
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Noun
1. living together (as spouses)
(synonym) living together
(hypernym) inhabitancy, inhabitation, habitation
(hyponym) concubinage
(derivation) cohabit, shack up

n. cohabitation

(n.)
The living together of a man and woman in supposed sexual relationship.
  

(n.)
The act or state of dwelling together, or in the same place with another.