Tai vs Kadai language

Tai and Kadai language both are nouns.

Word	Noun	Adjective	Verb	Adverb
Tai	Yes	Yes	No	No
Kadai language	Yes	No	No	No

As nouns, Kadai language is a hypernym of Tai; that is, Kadai language is a word with a broader meaning than Tai:

Tai: the most widespread and best known of the Kadai family of languages
Kadai language: a family of Sino-Tibetan languages spoken in southeastern Asia

Other hypernyms of Tai include Kadai, Kam-Tai.

Tai (noun)	Kadai language (noun)
the most widespread and best known of the Kadai family of languages	a family of Sino-Tibetan languages spoken in southeastern Asia
a native or inhabitant of Thailand

Tai (adjective)	Kadai language (adjective)
of or relating to Thailand
of or relating to the languages of the Thai people
of or relating to or characteristic of Thailand or its people