Triangle- A three-sided polygon. The sum of the angles of a triangle is 180 degrees.

Isosceles Triangle- A triangle having two sides of equal length.

Scalene Triangle- A triangle having three sides of different lengths.

Acute Triangle- A triangle having three acute angles or angles less than 90 degrees.

Obtuse Triangle- A triangle having an obtuse angle. One of the angles of the triangle measures more than 90 degrees.

Right Triangle- A triangle having a right angle. One of the angles of the triangle measures 90 degrees. The side opposite the right angle is called the hypotenuse. The two sides that form the right angle are called the legs. A right triangle has the special property that the sum of the squares of the lengths of the legs equals the square of the length of the hypotenuse. This is known as the Pythagorean Theorem.

Equilateral- A triangle with three equal segements or sides.

Equiangular- A triangle with three equal angles of 60^o.