# Jraph

This lesson offers an overview of Jraph, a library providing support for Graph Neural Networks (GNNs).

## Graph theory

Graph theory is a beautiful subject that has applications in many fields, including molecular structures, path planning, search engine optimization (SEO), and social media.

Let’s have a quick recap of graph theory.

### Basic terminology

A graph is a collection of **vertices** and **edges** connecting these vertices.
A directed graph contains directed edges.

$E(u,v) \ne E(v,u)$

A **loop** is an edge starting and terminating at the same vertex. $-$ $E(u,u)$

Two vertices $u$ and $v$ are **adjacent** if they are endpoints of $E(u,v)$ in an undirected graph. The edge $E(u,v)$ will be known as the **incident edge**.

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