Learner's definition of SIMILARITY
a quality that makes one person or thing like another
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
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]