Definition
We can split the word equilateral in two parts: equi meaning equivalent and lateral meaning side. So an equilateral triangle is simply a triangle whose three sides are all equal. Who knew English could help us in math?
Here's an example of an equilateral triangle:
all sides and angles are equal in this triangle
You'll notice that along with this triangle's sides, its three angles are also all equal. Since the sum of a triangle's angles is always 180 degrees, each angle in an equilateral triangle must measure 60 degrees. This is because we must divide 180 degrees evenly between the three angles: 180 / 3 = 60.