Acute triangle - all angles are acute (less than 90 degrees)

Obtuse triangle - one angle is obtuse ( more than 90 degrees)

Scalene triangle - no two sides are congruent

Isoscles triangle - at least two sides are congruent

Equilateral triangle - all three sides are congruent

Right triangle - one angle is right ( exactly 90 degrees)

Corollary - there can be at most one right or obtuse angle in any triangle

*Explorations with GSP