sim·i·lar·i·ty 
/ˌsɪməˈlerəti/ noun
plural sim·i·lar·i·ties /ˌsɪməˈlerəti/ noun : a quality that makes one person or thing like another [count] ▪ I doubt that these words are related beyond a similarity in sound. ▪ The books share a similarity of ideas. ▪ I see a lot of similarities in them. — often + between ▪ Have you noticed a similarity between these movies? ▪ We discussed the similarities between the author's books. [noncount] ▪ Looking at these fossils, I see some similarity to modern-day birds. ▪ I see very little similarity between your situation and his. ▪ Both women have two children and like sports but there the similarity ends. [=they are not alike in other ways]
