In the system of logic created by the philosopher Aristotle, the syncategorematic term is any word or group of words that describe a singular concept. Syncategorematic terms can combine to form a proposition. There are four kinds of these propositions. A term can be either distributive or non-distributive, and the proposition itself can be either affirmative or negative.
Distributive here means that the term refers to the whole of a set. _All_ of x as opposed to _some_ of x. Non-distributive means just the opposite, only referring to a portion of a set.
Affirmative propositions describe something by associating two terms. x _is_ y. A negative proposition describes something by dissociating the two terms. x _is not_ y.
So we have the following four possible combinations, forming propositions, each combination is designated by a letter.
"A" propositions are distributive and affirmative, and come in the form "all x is y"
"E" propositions are distributive but negative, and come in the form "no x is y"
"I" propositions are non-distributive and affirmative, and come in the form "some x is y"
"O" propositions are non-distributive but negative, and come in the form "some x is not y"