Nothing. These are all different words for the exact same thing, payments made to a former spouse for either a predetermined or undetermined amount of time to be used to financially support the former spouse. Regarding the three different words, it just depends what state you live in as each state uses one of the three primarily. In Missouri, the state statutes use the word maintenance, but many clients as well as attorneys use spousal support or alimony interchangeably with maintenance. However, it is important to be familiar with the word maintenance, because Judges, court forms and paperwork, and educational materials about the Missouri court process will utilize the word maintenance.