In the Old Testament, there was a lengthy, legal espousal period for a Jewish couple before they were married. This betrothal was much more binding than the western concept of engagement. If it was discovered that there had been fornication, the espousal could be legally broken with a writ of divorcement. Betrothal was, in Jewish law, as valid as a marriage.
The espoused couple, although they did not live together and the marriage was not yet consummated, was referred to as ‘husband’ and ‘wife’ as illustrated by Joseph and Mary in Matthew 1:18-19.