mnemotechnical vs mnemonic

mnemotechnical is not a noun while mnemonic is a noun.

Word	Noun	Adjective	Verb	Adverb
mnemotechnical	No	Yes	No	No
mnemonic	Yes	Yes	No	No

As adjectives, mnemotechnical and mnemonic are synonyms defined as:

mnemotechnical and mnemonic: of or relating to or involved the practice of aiding the memory

Other synonyms of mnemotechnical include mnemotechnic.

mnemotechnical (noun)	mnemonic (noun)
	a device (such as a rhyme or acronym) used to aid recall

mnemotechnical (adjective)	mnemonic (adjective)
of or relating to or involved the practice of aiding the memory	of or relating to or involved the practice of aiding the memory