A dominant person or thing is one that has power and influence over others.
In the group, she was the dominant, always leading the discussions and making decisions.
In genetics, a dominant trait or gene is one that is expressed in an organism's phenotype, masking the effect of a recessive trait or gene when present.
Brown eyes are a dominant trait, so they are more common in the population.
In music, the fifth note of the diatonic scale, which is the second most important note after the tonic.
The piece resolved beautifully on the dominant, creating a sense of anticipation.