The neighbour note (or auxiliary note) moves away from a consonant note and then returns to it. It is like the unaccented passing note in that it is usually on an unaccented part of the bar and this thus a relative unobtrusive dissonance.
Neighbour notes can appear on any note of a triad but must be no more than a major second away, hence the name. As with all the embellishments discussed on this site, the neighbour note can decorate any voice in a texture as in the example below.

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