Circle of fifths
Relationship among the 12 tones of the chromatic scale, their corresponding key signatures, and the associated major and minor keys; geometrical representation of relationships among the 12 pitch classes of the chromatic scale in pitch class space
In music theory, the circle of fifths is a way of organizing pitches as a sequence of perfect fifths. Starting on a C, and using the standard system of tuning for Western music (12-tone equal temperament), the sequence is: C, G, D, A, E, B, F♯ (G♭), C♯ (D♭), G♯ (A♭), D♯ (E♭), A♯ (B♭), E♯ (F), C. This order places the most closely related key signatures adjacent to one another. Wikipedia