1) Homomorphism 2) Similarity 1) Homomorphism 
• (n.) Similarity of form; resemblance in external characters, while widely different in fundamental structure; resemblance in geometric ground form. See Homophyly, Promorphology.
Ho'mo·mor`phy noun [ Homo- + Greek ... form.] (Biol.) Similarity of form; resemblance in external characters, while widely different in fundamental structure; resemblance in geometric ground form. See Homophyly , Promorphology . 
homomorphy 1. Similarity of form with different fundamental structure; specifically, superficial resemblance between organisms of different groups due to evolutionary convergence. 2. Resemblance in external characteristics, while widely different in fundamental structure.