chi vs letter of the alphabet

chi and letter of the alphabet both are nouns.

Word	Noun	Adjective	Verb	Adverb
chi	Yes	No	No	No
letter of the alphabet	Yes	No	No	No

As nouns, letter of the alphabet is a hypernym of chi; that is, letter of the alphabet is a word with a broader meaning than chi:

chi: the 22nd letter of the Greek alphabet
letter of the alphabet: the conventional characters of the alphabet used to represent speech

Other hypernyms of chi include alphabetic character, letter.

chi (noun)	letter of the alphabet (noun)
the circulating life energy that in Chinese philosophy is thought to be inherent in all things; in traditional Chinese medicine the balance of negative and positive forms in the body is believed to be essential for good health	the conventional characters of the alphabet used to represent speech
the 22nd letter of the Greek alphabet