Common noun

iron (Fe)

Common noun

steel

Nouns which may take the genitive case particle 'no'; Common noun

iron (will, discipline, lady, etc.)

Abbreviation; Common noun; Noun, used as a suffix; Noun, used as a prefix

railway

Colloquial; Noun, used as a suffix

railway enthusiast

steel

trigger (of a gun, etc.)

trigger (for something); immediate cause

iron plate; steel plate

Colloquial

sure thing; certain winner

railroad; railway; rail transport

gun; firearm

Sumo

wooden pole that wrestlers strike in practice

Colloquial

puffer fish

iron grill; iron grille; iron lattice; iron bars

Colloquial

prison

Common noun

iron wall; impregnable fortress

Nouns which may take the genitive case particle 'no'

impregnable; invulnerable; unassailable; cast-iron

Abbreviation

subway; metro; underground (railway)

made of iron