Graph: Does simple path mean no repeated vertices or edges?

2.3k Views Asked by At

I'm reading Discrete Mathematics and It's application, Rosen, 7-th ed.. By the definition, a simple path of undirected graph contains no repeated edges

enter image description here

But in the proof of following theorem it seems like the definition becomes no repeated vertices

enter image description here

And in the remark following the definition it says: When this terminology is used, the terminology path is often used for a trail with no repeated vertices, $\color{red}{\textrm{conflicting}}$ with the terminology in Definition 1.

enter image description here

But my understanding is

$$\textrm{repeated edges} \implies \textrm{repeated vertices}$$

enter image description here

-

There are two possible cases with definition 1, and the subscripts of the resulting path of both are the same as the one in the book, but in one case the path will be cut into two with the statement [...] by deleting the edges correspoding to the vertex sequence $x_i,\dots, x_{j-1}$.

enter image description here enter image description here