ECM vs EW

ECM and EW both are nouns.

Word	Noun	Adjective	Verb	Adverb
ECM	Yes	No	No	No
EW	Yes	No	No	No

As nouns, EW is a hypernym of ECM; that is, EW is a word with a broader meaning than ECM:

ECM: electronic warfare undertaken to prevent or reduce an enemy's effective use of the electromagnetic spectrum
EW: military action involving the use of electromagnetic energy to determine or exploit or reduce or prevent hostile use of the electromagnetic spectrum

Other hypernyms of ECM include electronic warfare.

ECM (noun)	EW (noun)
electronic warfare undertaken to prevent or reduce an enemy's effective use of the electromagnetic spectrum	military action involving the use of electromagnetic energy to determine or exploit or reduce or prevent hostile use of the electromagnetic spectrum