An a priori hypothesis is one that is generated prior to a research study taking place. A priori hypotheses are distinct from a posteriori hypotheses, which are generated after an observable phenomenon occurs.
"A priori" is a Latin phrase that stands for "what comes before." These hypotheses are a typical part of the scientific method in that they are formed based on previously assumed conclusions. These types of hypotheses are deduced from these assumptions. "A posteriori" is a hypothesis generated based on induction. It is formed based on an empirical observation and then attempts to hypothesize the underlying cause of the observation.