break down vs breakdown

break down is not a noun while breakdown is a noun.

Word	Noun	Adjective	Verb	Adverb
break down	No	No	Yes	No
breakdown	Yes	No	No	No

break down (noun)	breakdown (noun)
	the act of disrupting an established order so it fails to continue
	an analysis into mutually exclusive categories
	a cessation of normal operation
	(biology) the process of decay caused by bacterial or fungal action
	(chemistry) separation of a substance into two or more substances that may differ from each other and from the original substance
	a mental or physical breakdown

break down (verb)	breakdown (verb)
collapse due to fatigue, an illness, or a sudden attack
stop operating or functioning
separate (substances) into constituent elements or parts
make a mathematical, chemical, or grammatical analysis of; break down into components or essential features
make ineffective
cause to fall or collapse
lose control of one's emotions
fall apart