yagi vs directional antenna

yagi and directional antenna both are nouns.

Word	Noun	Adjective	Verb	Adverb
yagi	Yes	No	No	No
directional antenna	Yes	No	No	No

As nouns, directional antenna is a hypernym of yagi; that is, directional antenna is a word with a broader meaning than yagi:

yagi: a sharply directional antenna
directional antenna: an antenna that transmits or receives signals only in a narrow angle

yagi (noun)	directional antenna (noun)
a sharply directional antenna	an antenna that transmits or receives signals only in a narrow angle