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In music theory, the dominant or dominant note (second most important) of a key is that which is a perfect fifth above the tonic; in just intonation the note whose pitch is 1.5 times the frequency of the tonic note's pitch and in twelve tone equal temperament is 7 semitones or 700 cents above the tonic. This pitch can also be called the third harmonic of the harmonic series. The dominant of a church mode was the tenor or reciting tone of psalm tones. The dominant is also the diatonic function of the dominant note and chord.

In biology and in populations, a group, pair or, or individual can be the dominant animal in a group. Dominant animals take a higher position in a "pecking order", and may be the only animals allowed to breed within a group.

In genetics, a dominant gene is one that is expressed when heterozygous with a recessive allele of the gene. It is a feature of diseases that inherit in an autosomal dominant fashion.

In decision theory, one estimator dominates another if it always achieves lower risk.

In BDSM, Dominant is a more precise term for a top in BDSM - see dominant (BDSM)

In Genetics, it covers up recessive unless it is incomplete dominance.