Greater tone

major second

Inverse	minor seventh
Name
Other names	whole tone, whole step
Abbreviation	M2
Size
Semitones	2
Interval class	2
Just interval	9:8 or 10:9
Cents
Equal temperament	200
24 equal temperament	200
Just intonation	204 or 182

In Western music theory, a major second (sometimes also called whole tone) is a second spanning two semitones ( Play ). A second is a musical interval encompassing two adjacent staff positions (see Interval number for more details). For example, the interval from C to D is a major second, as the note D lies two semitones above C, and the two notes are notated on adjacent staff positions. Diminished, minor and augmented seconds are notated on adjacent staff positions as well, but consist of a different number of semitones (zero, one, and three).

The major second is the interval that occurs between the first and second degrees of a major scale, the tonic and the supertonic. On a musical keyboard, a major second is the interval between two keys separated by one key, counting white and black keys alike. On a guitar string, it is the interval separated by two frets. In moveable-do solfège, it is the interval between do and re. It is considered a melodic step, as opposed to larger intervals called skips.

...
Wikipedia