graph theory

1. a graph whose vertices and edges are a subset of some graph G
4. a vertex whose degree is zero is ....
7. a collection of trees
12. a graph with no vertices and no edges
14. a walk that uses every edge exactly once
17. graphs that have the same shape (or can be squished into the same shape)
18. an edge such that if you were to cut it the graph would fall into more pieces
22. number of edges that a vertex is connected to
23. a graph whose vertices all have the same degree
24. a vertex in a directed graph with no outgoing edges
25. a graph that is in one piece
26. number of edges going out of a vertex in a directed graph
27. a vertex in a directed graph with no incoming edges
28. a graph in which vertices have weights

2. a matrix whose rows and columns are indexed by vertices of graph, showing where the edges of the graph are
3. a graph G' that has the same vertices as some graph G and edges precisely where G has no edges
5. a closed walk without repeated vertices
6. number of edges coming into a vertex in a directed graph
8. (undirected case) connected acyclic graph
9. a walk that covers all vertices of graph exactly once
10. finite or infinite sequence of edges which joins a sequence of vertices
11. a vertex in a tree with degree 1
13. a directed graph or its subgraph in which every vertex is reachable from others
15. a graph whose vertices can be divided into two disjoint sets such that no edges are between vertices in the same set
16. a subgraph of a graph G that is a tree and contains all vertices of G
19. a graph whose edges do not go both ways
20. a structure amounting to a set of objects in which some pairs of the objects are in some sense "related", consisting of vertices and edges
21. an edge whose endpoints are at the same vertex