Similarity

From Wikipedia, the free encyclopedia

Similarity is some degree of symmetry in either analogy and resemblance between two or more concepts or objects. The notion of similarity rests either on exact or approximate repetitions of patterns in the compared items. In the case of approximate repetitions we talk about statistical similarity as found in a fractal and its parts. Finding similarities or distinguishing between dissimilarities depends on the faculties of pattern recognition and disambiguation, respectively.

Different fields provide differing definitions of similarity:

• In mathematics:
  • Similarity (geometry)
  • Similar matrices
• In psychology, similarity (psychology)
• In music, Musical similarity
• In computational linguistics, semantic similarity
• Natural similarity

In philosophy, similarity is defined as sharing properties. So the sky is similar to the sea, for example, because the sky and the sea both share the property of being blue.

This definition has some interesting consequences. First, it follows that resemblance is reflexive, since everything shares its own properties. Second, it follows that resemblance is symmetric, since if x shares properties with y then y shares those same properties with x. Third, qualitative identity turns out to be a limiting case of resemblance, since qualitative identity is defined as sharing all rather than some properties.