mixolydian

(noun)
1) the major scale, but the 7th note is lowered by a semitone.
2) the major scale, but you treat the 5th note as the root.

A: What key is “Hey Jude” by The Beatles in?
B: It’s in Mixolydian.

Lydian

(noun)
1) the major scale, but the 4th note is raised by a semitone
2) the major scale, but you treat the 4th note as the root

(adjective)
relating to Lydia, an ancient region of western Asia Minor, south of Mysia and Caria.

“The Lydian mode has a raised note instead of lowered ones. It sounds bright and carefree. Awfully carefree.”

phrygian

(noun)
1) the minor scale, but the 3rd note is lowered by a semitone
2) the major scale, but you treat the 3rd note as the root

(adjective)
relating to Phrygia, an ancient region in west central Asia Minor, to the south of Bithynia.

A: Hey try playing Locrian with a natural fifth
B: Dude it’s just Phrygian, then

ionian

(noun)
1) the major scale - so we won’t confuse it with major in chords
2) a member of an ancient Hellenic people inhabiting Attica, parts of western Asia Minor, and the Aegean islands in preclassical and classical times. Colonised the islands that became known as the Ionian islands.

- a native or inhabitant of the Ionian islands.

(adjective)
relating to the Ionians, Ionia, or the Ionian islands

A: Yo what key is this song in?
B: E flat ionian
A: …it’s E flat major isn’t it
B: well yes, but actually no