pitkittäisistä

Pitkittäisistä is the elatiivin monikko form of the Finnish adjective pitkittäinen, which means longitudinal or spanning along the length. In Finnish, adjectives of the -inen type decline like nouns, and the elatiivin (elative) plural form ends with -isistä. Thus pitkittäisistä translates roughly to “from the longitudinal ones” or “of the longitudinal ones,” depending on the context.

Grammatical overview is useful for understanding its usage. The base adjective pitkittäinen has several plural forms: nominative pitkittäiset, genitive pitkittäisten, partitive pitkittäisiä, inessive pitkittäisissä, and elative pitkittäisistä. The elative plural is used to indicate origin or source from a set of items described as longitudinal. For example, in research phrases you might encounter pitkittäisistä näytteistä or pitkittäisistä mittauksista, meaning data or measurements obtained from longitudinal samples or measurements.

Usage and contexts. pitkittäisistä is common in scientific, statistical, and technical Finnish when referring to multiple longitudinal items, such as studies, samples, or measurements. It helps specify that the referenced information comes from longitudinal sources rather than cross-sectional ones. Because it is a case form, its grammatical compatibility depends on the noun it modifies and the overall syntactic role in the sentence.

See also. Finnish grammar and declension of adjectives; longitudinal data and longitudinal studies in science; related forms of the adjective pitkittäinen.

In sum, pitkittäisistä is a technical inflected form used to express origin or relation to longitudinal items within Finnish prose, particularly in descriptive or analytic contexts.