Formal Context

A formal context is a triple of sets (O,A,I)
where

O is a set of objects
A is a set of attributes
I is a binary relation between A and O (O X A Matrix)

The notation oIa,
where
o is a member of O
a is a member of A

(o,a) is a member of I

More simply, the formal context can be visualized as a vector space model
where each row represents an object from O and each column represents an attribute from A. Each matrix element presents the occurence/existence of attribute a in object o. Various variant of such a model exists with the different being the matrix element function. For example, the matrix element value might represent the degree of significant of the attribute a in object o, instead of simply representing the existence.