4. A subgraph of a graph G = (V;E) is a graph
H = (W; F), where W⊆V and
F ⊆ E.
A subgraph H of G is a proper subgraph of
G if H ≠ G.
5. Note. if we remove one edge from G then H=G-{e} is also
a subgraph of G
Note. if we remove one vertex from G then H=G-{v} is also
a subgraph of G
Note. if we add one edge in G then G is a subgraph of H =
G + {e}
Note. if we add one vertex in G then G is a subgraph of H
= G + {v}