kierteinen

Kierteinen is a Finnish adjective meaning spiral, helical, twisted, or threaded. It is derived from the noun kierre, which denotes a twist, coil, or thread, and is formed with the common adjectival suffix -inen. The word describes objects that have a helical shape or a screw-like thread, but it can also refer to anything that is twisted or coiled in appearance.

In technical and engineering language, kierteinen is used to indicate a threaded feature or a spiral form. For example, a kierteinen ruuvi would be a threaded bolt, and a kierteinen jousi can describe a coil spring. The adjective agrees with the noun it modifies in number and case, and it can be used both attributively (kierteinen putki) and predicatively (Ruuvi on kierteinen).

Beyond engineering, kierteinen can describe patterns, lines, or surfaces that show a spiral or twisted arrangement, such as decorative motifs or mathematical spirals, although in everyday Finnish more common terms such as kiertynyt or mutkikas may be used depending on nuance.

Etymology: from kierre (twist, turn, thread) plus -inen, forming an attributive adjective. See also related terms kierre, kiertymä, kiertää. In standard Finnish, kierteinen appears in dictionaries and technical texts and is understood to convey coiling or threading. It is not a widely used standalone concept outside descriptions of form, but remains part of the language’s technical vocabulary.