Can we say in general, [*Treewidth*](https://en.wikipedia.org/wiki/Treewidth) of every graph is less than or equal to number of vertices in that graph?
Is there any other general relation between *Treewidth* and [*Order*](http://mathworld.wolfram.com/GraphOrder.html) of graphs?



What is the relation between Treewidth and Order of graph?
The treewidth of an $n$-vertex graph is always at most $n-1$ (because it is defined as one less than the cardinality of the largest bag in an optimal tree decomposition, and each bag is a set of $n$ or fewer vertices). It is exactly $n-1$ in the case of a complete graph, and can be as small as $0$ for an independent set, so there is no tighter relation possible between treewidth and $n$.


