A linear pair is a pair of adjacent angles formed when two lines intersect. In the figure, ∠ 1 and ∠ 2 form a linear pair. So do ∠ 2 and ∠ 3 , ∠ 3 and ∠ 4 , and ∠ 1 and ∠ 4 .

A linear pair is a pair of adjacent angles whose non-adjacent sides form a line. In the diagram above, ∠ABC and ∠DBC form a linear pair.

In simpler terms, two angles form a linear pair if they are adjacent and their non-shared sides form a straight line.

Linear Pair Theorem: If two angles form a linear pair, their measures sum 180. Mathematically, if ∠A and ∠B form a linear pair, then: Measure of ∠A + Measure of ∠B = 180°

Linear pair of angles are formed when two lines intersect each other at a single point. The angles are said to be linear if they are adjacent to each other after the intersection of the two lines.