emergency; crisis; imminent danger
Refers to a critical situation requiring immediate action. Often used in compound nouns like 危急存亡 (life-or-death crisis) or 危急の際 (in case of emergency).
In case of emergency, please press this button.
The country is facing a life-or-death crisis.
Vulnerable (conservation status); VU
Obsolete term for the IUCN conservation status 'Vulnerable'. The modern standard term is 絶滅危惧 (ぜつめつきぐ) or more specifically 危急種 (ききゅうしゅ) in some contexts, but 危急 alone is no longer used this way.
See also: 絶滅危惧
In older literature, 危急 is sometimes used to mean 'Vulnerable' in the conservation sense.
In case of an emergency, first make sure you are safe.
The country was on the brink of a fiscal crisis.
The siren was signaling an emergency.
絶滅危惧 is the modern standard term for the IUCN 'Vulnerable/Threatened' conservation status, replacing the now-obsolete use of 危急 in that sense.
危機 broadly means 'crisis' and is used for personal, national, or economic crises, whereas 危急 stresses that the danger is imminent and requires immediate action.
Compound of 危 (danger) and 急 (urgent). The word has been used in formal and literary Japanese to denote a critical emergency since at least the early modern period.