The Different between Vertex and Vertices

The term of vertex and vertices are so confusing for me. 

At first I think both are so much different, but after googling a lil' bit, I found out that :

Vertex is a single point in 3D space, it has 3 dimensional directions (x,y,z axis). When connected to others, it'll form edge, face, curve, and polygon.

Vertices is a plural form of vertex (that's very brief and clear explanation).

Oh yeah, the source where I learn them are in 3drender.com and blender 3d wikibook.

I think that's all. Pretty easy, isn't it? So, how about you? What is the difficult term that you think is very hard to comprehend in learning 3D? Share it below, so maybe I can help you out.

Thanks for reading.

Picture by Aditia A. Pratama