language vs toponymy

language and toponymy both are nouns.

Word	Noun	Adjective	Verb	Adverb
language	Yes	No	No	No
toponymy	Yes	No	No	No

As nouns, toponymy is a hyponym of language; that is, toponymy is a word with a more specific, narrower meaning than language:

Other hyponyms of language include markup language, toponomy.

language (noun)	toponymy (noun)
the mental faculty or power of vocal communication	the branch of lexicology that studies the place names of a region or a language
the cognitive processes involved in producing and understanding linguistic communication	the nomenclature of regional anatomy
a systematic means of communicating by the use of sounds or conventional symbols
(language) communication by word of mouth
the text of a popular song or musical-comedy number
a system of words used to name things in a particular discipline