äkillisen

äkillinen is a Finnish adjective meaning sudden, abrupt, or acute in the sense of something arising quickly or without warning. It is used to describe events, changes, or sensations that start abruptly, such as a sudden pain, a rapidly developing situation, or an unforeseen change. In medical contexts it often conveys the sense of an onset that is rapid, though the more technical term for some conditions is akuuttinen or akuuttia.

The form äkillisen is the genitive singular of äkillinen. Finnish adjectives inflect to agree with the noun they modify in number and case. Other common forms include äkillinen (nominative singular), äkillistä (partitive singular), äkilliset (nominative plural), äkillisten (genitive plural), and äkillisiä (partitive plural). The adverbial form is äkillisesti, and the corresponding noun for the quality is äkillisyys.

Usage notes: äkillinen emphasizes suddenness or abrupt onset rather than overall severity. It is widespread in written Finnish and is found in medical, descriptive, and journalistic contexts. When describing a pain or symptom, speakers may choose different inflections to fit the sentence structure, for example äkillisen kivun (genitive) or äkillistä kipua (partitive with experiencer verbs).

Etymology and related terms: the word is native Finnish, with related forms including äkillisesti (adverb) and äkillisyys (the quality of being sudden). Related concepts include yllättävä (unexpected) and äid? more generally, the medical term for abrupt onset is often expressed with äkillinen in plain language, while akuuttia or akuutti may appear in formal medical terminology.

See also: akuutti, yllättävä, äkillisyys.