Distribution of Terms  Applied to the membership of categories distribution means that all members in a category are being referred to; if there are 5,000 brains surgeons in the world, a distributed term makes reference to all 5,000 of them and the same term in undistributed form makes reference to some portion of that 5,000 from 1 to 4,999.

Note that distribution does not refer to how terms are spread around, thrown out, or placed within a categorical argument.  Instead of telling us where each term of an argument may be found, distribution tells us how many members each term refers to. In the same argument, surgeons may be distributed in one statement and undistributed in another.  Each term must be considered individually to determine its distribution. 

Distribution of terms can be discovered by working with two circle Venn diagrams, by memorizing a chart of the AEIO forms indicating distribution, or by thoughtful inference using the following principles which focus on the subject and predicate terms separately:

                        Distribution of the Subject Term is defined by the quantifier of the term

• "All" indicates a distributed term
• "Some" indicates an undistributed term

                        Distribution of the Predicate Term is defined by the quality of the statement

• If the statement is an affirmation, the predicate term is undistributed
• If the statement is a denial, the predicate term is distributed.