A 90 degree angle, also known as a right angle, looks like the corner of a square or rectangle. The two lines that form the 90 degree angle are perpendicular to one another.

A 140 degree angle is about half way between a 90 degree angle, which has lines that are perpendicular to each other, and a 180 degree angle, which is a straight line. A 140 degree angle is an obtuse angle which has a line a little over half way between the 90 degree and 180 degree angles.

A 45-degree angle looks like half of a 90-degree angle. It looks exactly like one straight line with one horizontal line of the bottom, similar to half a square.