brainwave vs delta wave

brainwave and delta wave both are nouns.

Word	Noun	Adjective	Verb	Adverb
brainwave	Yes	No	No	No
delta wave	Yes	No	No	No

As nouns, delta wave is a hyponym of brainwave; that is, delta wave is a word with a more specific, narrower meaning than brainwave:

brainwave: (neurophysiology) rapid fluctuations of voltage between parts of the cerebral cortex that are detectable with an electroencephalograph
delta wave: the normal brainwave in the encephalogram of a person in deep dreamless sleep; occurs with high voltage and low frequency (1 to 4 hertz)

Other hyponyms of brainwave include alpha rhythm, alpha wave, beta rhythm, beta wave, delta rhythm, theta rhythm, theta wave.

brainwave (noun)	delta wave (noun)
the clear (and often sudden) understanding of a complex situation	the normal brainwave in the encephalogram of a person in deep dreamless sleep; occurs with high voltage and low frequency (1 to 4 hertz)
(neurophysiology) rapid fluctuations of voltage between parts of the cerebral cortex that are detectable with an electroencephalograph