Isosceles
Both of them have 3 sides but an isosceles triangle has only 2 equal sides whereas an equilateral triangle has 3 equal sides.
They are both are triangles having 3 sides and 3 interior angles that add up to 180 degrees but an isosceles triangle has two equal sides whereas a scalene triangle has no equal sides.
Both sides of one of its diagonals
they could both have sides and angles....
A square is a rectangle.A square is not a triangle. Triangles only have 3 sides.