Let's fill in the blanks to make the statements true step-by-step:
1. If there is at least one edge connecting two vertices in a graph, the vertices are called adjacent.
2. A sequence of such vertices and the edges connecting them is called a path.
3. If this sequence of vertices and connecting edges begins and ends at the same vertex, it is called a cycle.
Now, let's put it all together:
If there is at least one edge connecting two vertices in a graph, the vertices are called adjacent. A sequence of such vertices and the edges connecting them is called a path. If this sequence of vertices and connecting edges begins and ends at the same vertex, it is called a cycle.
These definitions are foundational in graph theory, which is a field of mathematics and computer science dealing with graphs, which are structures made up of vertices (or nodes) connected by edges.