“The word “graph” has (at least) two meanings in mathematics.
“In elementary mathematics, “graph” refers to a function graph or “graph of a function,” i.e., a plot.
“In a mathematician’s terminology, [especially in graph theory], a graph is a collection of points and lines connecting some (possibly empty) subset* of them. The points of a graph are most commonly known as graph vertices, but may also be called “nodes” or simply “points.” Similarly, the lines connecting the vertices of a graph are most commonly known as graph edges, but may also be called “arcs” or “lines.”” (“Graph,” WolframMathWorld, retrieved 6/25/2020)
Graphs seem to be used to show how different parts of a thing or things are connected with each other.
If interested in getting a better idea of what graphs are, a good starting point would be to read “Graph,” from WolframMathWorld, (retrieved 6/25/2020) and, after the other link, “Graph (discrete mathematics),” from Wikipedia (retrieved 6/25/2020), especially the section “Properties of graphs.”
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*What is the Gist of a “Subset”?
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Disclaimer:
I am not a professional in this field, nor do I claim to know all of the jargon that is typically used in this field. I am not summarizing my sources; I simply read from a variety of websites until I feel like I understand enough about a topic to move on to what I actually wanted to learn. By definition, none of these posts address every aspect of a topic. If I am inaccurate in what I say or you know a better, simpler way to explain a concept, I would be happy to hear from you :).
Would you expand on this?
Sure! What specifically would you like me to expand on?