2 added 78 characters in body edited Jul 9 '15 at 17:41 D.W.♦ 105k1414 gold badges133133 silver badges309309 bronze badges Yes, I suppose you cancould, though it might be viewed as a somewhat informal usage of the term "topology". A "Shape" would probably be a better word, as @Raphael suggests. A more precise way would be to say that these two trees are not isomorphic. Background: Two graphs $$G,G'$$ are considered isomorphic if there exists a map $$f:V \to V'$$ that is a graph isomorphism. Since any tree can be viewed as a graph, you can consider two trees to be isomorphic if they are isomorphic as graphs. One can also define a natural notion of a tree isomorphism directly; this happens to be equivalent to the notion of a graph isomorphism for unrooted trees, but is slightly different (and more appropriate to use) for rooted trees. You can read more about isomorphisms in standard sources. Yes, you can, though it might be viewed as a somewhat informal usage of the term "topology". A more precise way would be to say that these two trees are not isomorphic. Background: Two graphs $$G,G'$$ are considered isomorphic if there exists a map $$f:V \to V'$$ that is a graph isomorphism. Since any tree can be viewed as a graph, you can consider two trees to be isomorphic if they are isomorphic as graphs. One can also define a natural notion of a tree isomorphism directly; this happens to be equivalent to the notion of a graph isomorphism for unrooted trees, but is slightly different (and more appropriate to use) for rooted trees. You can read more about isomorphisms in standard sources. Yes, I suppose you could, though it might be viewed as a somewhat informal usage of the term "topology". "Shape" would probably be a better word, as @Raphael suggests. A more precise way would be to say that these two trees are not isomorphic. Background: Two graphs $$G,G'$$ are considered isomorphic if there exists a map $$f:V \to V'$$ that is a graph isomorphism. Since any tree can be viewed as a graph, you can consider two trees to be isomorphic if they are isomorphic as graphs. One can also define a natural notion of a tree isomorphism directly; this happens to be equivalent to the notion of a graph isomorphism for unrooted trees, but is slightly different (and more appropriate to use) for rooted trees. You can read more about isomorphisms in standard sources. 1 answered Jul 8 '15 at 22:24 D.W.♦ 105k1414 gold badges133133 silver badges309309 bronze badges Yes, you can, though it might be viewed as a somewhat informal usage of the term "topology". A more precise way would be to say that these two trees are not isomorphic. Background: Two graphs $$G,G'$$ are considered isomorphic if there exists a map $$f:V \to V'$$ that is a graph isomorphism. Since any tree can be viewed as a graph, you can consider two trees to be isomorphic if they are isomorphic as graphs. One can also define a natural notion of a tree isomorphism directly; this happens to be equivalent to the notion of a graph isomorphism for unrooted trees, but is slightly different (and more appropriate to use) for rooted trees. You can read more about isomorphisms in standard sources.