chemical defense vs chemical defence

chemical defense and chemical defence both are nouns.

Word	Noun	Adjective	Verb	Adverb
chemical defense	Yes	No	No	No
chemical defence	Yes	No	No	No

As nouns, chemical defense and chemical defence are synonyms defined as:

chemical defense and chemical defence: procedures involved in taking defensive measures against attacks using chemical agents

chemical defense (noun)	chemical defence (noun)
procedures involved in taking defensive measures against attacks using chemical agents	procedures involved in taking defensive measures against attacks using chemical agents