Definition of music mode notion
In music, modes are ways of ordering music notes. For a given and named mode, each notes of the modes have specifics intervals starting from the tonic (first note)
Example of famous modes
Below are some famous modes:
Ionian Mode:
All major scales are in fact transpositions of the Ionian mode.
Major pentatonic mode
Major pentatonic mode contains only 5 notes.
Whole tone scale
Intervals between 2 successive notes are always 1 whole step 
As you can see and hear, a mode can contain 5, 6, 7, or less or more notes.
Others articles from this category:
Modern Western modes
Learn modern Westerns modes: Ionian mode, Dorian mode, Phrygian mode, Lydian mode, Mixolydian mode, Aeolian mode, and Locrian mode.
Pentatonic scale
Pentatonic scale: Learn the notion of major pentatonic scale and minor pentatonic scale. Learn how is made pentatonic scales, see example of pentatonic scales.
Whole-tone scale
Whole-tone scale, definition and examples. The whole-tone scale is one of the modes of limited transposition, because there is only transposition of this mode.
Blues scale
Blues scale explained. See the relationship between blues scale and minor pentatonic scale. Learn how to play and how to use blues scale and its transpositions
Modes of limited transposition
Modes of limited transposition are modes for which transpositions possibilities are limited. Learn all modes of limited transposition
External links :
1 - https://musicterms.artopium.com/m/Mode.htm
2 - https://en.wikipedia.org/wiki/Mode_(music)
3 - https://www.dolmetsch.com/musictheory31.htm#modes