stain vs iron mould

stain and iron mould both are nouns.

Word	Noun	Adjective	Verb	Adverb
stain	Yes	No	Yes	No
iron mould	Yes	No	No	No

As nouns, iron mould is a hyponym of stain; that is, iron mould is a word with a more specific, narrower meaning than stain:

Other hyponyms of stain include scorch, bloodstain, iron mold, mud stain, oil stain, tarnish.

stain (noun)	iron mould (noun)
an act that brings discredit to the person who does it	a spot caused the staining with rust or ink
a soiled or discolored appearance
a symbol of disgrace or infamy
anything regarded as making something unclean
(microscopy) a dye or other coloring material that is used in microscopy to make structures visible

stain (verb)	iron mould (verb)
produce or leave stains
color with a liquid dye or tint
color for microscopic study
make dirty or spotty, as by exposure to air; also used metaphorically