Question

What does isosceles mean in geometry?

Answer 1

The word "isosceles" is, mostly, used referring to triangles with two sides equal in length

Explanation:

Here are major properties of isosceles triangles.

Draw altitude `h` from the vertex where two congruent sides `b` and `b` intersect.
It divides our triangle into two right triangles that share a cathetus `h` and have congruent hypotenuses `b` and `b`.

These triangles are congruent by cathetus and hypotenuse and, therefore altitude `h` is also a median of base `a` and an angle bisector of the angle at the top.

Consequently, two angles at the base of this isosceles triangle are also congruent.