Major & Minor 3rd

Major vs. minor — the defining difference

Prove it — just do the practice exercise.
C → E 4 semitones
C (root) E (Maj 3rd)
The third is the most important interval:

Major 3rd = 4 semitones → defines major character
Minor 3rd = 3 semitones → defines minor character

Example: C → E = major 3rd (major)
C → Eb = minor 3rd (minor)

Every chord contains a third — it tells you whether it's major or minor.