The single identifying feature of Lydian chords and the Lydian mode is the augmented 4th interval, also known as the sharp 11 (#11). To be even more specific, a Lydian chord is a major triad with the addition of an augmented 4th.
What is F Lydian?
The F Lydian is a mode of the C Major Scale. It contains exactly the same notes, but starts on another note. The F Lydian is the same as the F Major apart from one note, the fourth in the scale. F, Fmaj7, F6, F6/9, Fmaj9, Fmaj13. G, G7, G6, G6/9, G9, G11, G13.
What notes are in F Lydian mode?
2. Chords in the Lydian mode. The notes of an F chord are F, A and C – all of which appear in F Lydian (F G A B C D E) so the chord and the mode are guaranteed to sound good when played together. However, to bring out the Lydian flavour you need a #4 interval such as Fmaj7#11, Fsus#4 or Fadd#11.