An abandonment spouse is a person in a marriage who was purposely left by their spouse with no intention of returning. In order to prove that a spouse has been abandoned, a court usually requires more factual circumstances than just once spouse leaving another.
In "no-fault" states, there isn't a need to list a specific reason for a couple to get a divorce. In these states, if one person wants a divorce, the court will grant it. In "fault" states, the courts will require a specific reason for granting a divorce. In those states, abandonment is viewed as a valid reason. Typically, abandonment is seen as having taken place by the court of the spouse has been gone for over a year or if the spouses do not agree on the spouse moving out.