killer vs suicide

killer and suicide both are nouns.

Word	Noun	Adjective	Verb	Adverb
killer	Yes	No	No	No
suicide	Yes	No	No	No

As nouns, suicide is a hyponym of killer; that is, suicide is a word with a more specific, narrower meaning than killer:

killer (noun)	suicide (noun)
predatory black-and-white toothed whale with large dorsal fin; common in cold seas	the act of killing yourself
a difficulty that is hard to deal with	a person who kills himself intentionally
someone who causes the death of a person or animal
the causal agent resulting in death