a priori

/ɑ priˈɔri/

/ɒ priˈɔri/

A priori literally means "from before." If you know how many red, white, and blue gum balls are in the gum ball machine, this a priori knowledge can help you predict the color of the next ones to be dispensed.

In Latin a priori means “what comes first.” A priori understandings are the assumptions that come before the rest of the assessment, argument, or analysis. If you are making an argument that pre-school children who are read to at home by family members come to school better prepared to learn, the a priori understanding is that children learn by hearing before they are able to read.

Definitions of a priori

1. adjective

   involving deductive reasoning from a general principle to a necessary effect; not supported by fact
   “an a priori judgment”

   synonyms:

   analytic, analytical

   of a proposition that is necessarily true independent of fact or experience

   deductive

   involving inferences from general principles

   antonyms:

   a posteriori

   involving reasoning from facts or particulars to general principles or from effects to causes

   synthetic, synthetical

   of a proposition whose truth value is determined by observation or facts

   inductive

   of reasoning; proceeding from particular facts to a general conclusion
2. adjective

   based on hypothesis or theory rather than experiment
   synonyms:

   theoretic, theoretical

   concerned primarily with theories or hypotheses rather than practical considerations
3. adverb

   derived by logic, without observed facts
   antonyms:

   a posteriori

   derived from observed facts