A reciprocal, parallel or complementary relationship between two or more comparable objects.
An isomorphism from a projective space to the dual of a projective space, often to the dual of itself.
One of the several measures of the linear statistical relationship between two random variables, indicating both the strength and direction of the relationship.
A literary work which brings together or arranges systematically parallel passages of historians respecting the same events, and shows their agreement or consistency.
A pleasing combination of elements, or arrangement of sounds.
The relationship between two distinct musical pitches (musical pitches being frequencies of vibration which produce audible sound) played simultaneously.
The academic study of chords.
Agreement or accord.
Two or more notes played simultaneously to produce a chord.