Similarity (noun)

1. The state or fact of being similar.
2. A thing that is similar to another.
3. A resemblance in appearance, character, or behaviour.
4. The quality of being alike.
5. A similarity of function or structure.

Origin:

Late 16th century: from french similarité or latin similaritas, from similaris (see similar).

Examples:

1. There is a similarity between the two paintings.
2. There is a similarity in the way they think.
3. The similarity is striking.
4. There is a similarity in their names.
5. The similarity of their faces is uncanny.