- Closeness of appearance to something else.
- (philosophy) The relation of sharing properties.
- 1859–1860, William Hamilton, H[enry] L[ongueville] Mansel and John Veitch, editors, Lectures on Metaphysics and Logic […], volume (please specify |volume=I to IV), Edinburgh; London: William Blackwood and Sons, OCLC 648725:
- Hardly is there a similarity detected between two or three facts, than men hasten to extend it to all.
- (mathematics) A transformation that preserves angles and the ratios of distances
- (mathematics, linear algebra) The property of two matrices being similar.
closeness of appearance