What Is The Vertex Of A Triangle?

A triangle has 3 vertexes. The vertex is where 2 lines meet.

Vertex is the corner of triangle. Its plural is vertices or vertexes. Triangle has 3 vertices. Similarly, square has 4 vertices OR 4 corners

The vertex is the corner of the triangle. My geometery teacher taught my class by using a bit of a crude analogy but it definetley stuck in everyone's minds. The lines of the triangle is the legs and the V is the vertex and when looking at it the corner is an upside down V. Hopefully you can remember it now.
As for squares they're just the corners, no catchy phrases for that one.

A corner in which the lines of 2 sides meet, at the tip

Vertex is the corner of triangle. Its plural is vertices or vertexes. Triangle has 3 vertices. Similarly, square has 4 vertices OR 4 corners.
They can be names as any letters of english language. E.g. A,B, C , D.

Sides are the distance between two vertices e.g. Side AB, side BC

Corner

Corners