þessu

þessu is an Icelandic word form functioning as the dative singular of the demonstrative determiner þessi, meaning “this.” It is used when the noun it modifies is in the dative case, often in phrases that describe a thing or matter related to location, possession, or context. For example, in phrases like í þessu máli (in this matter) or með þessu (with this), the form þessu marks the reference as being in the dative.

In usage, þessu typically appears with a broad range of neuter, masculine, or feminine nouns depending on the syntactic requirements of the sentence. It is part of a larger demonstrative paradigm in Icelandic that marks distance and definiteness, and it is frequently found in written and spoken Icelandic. The specific dative form is one of several case forms that the demonstrative adjective inherits through inflection.

Etymology and orthography: þessu derives from the same demonstrative root as þessi, with the dative singular ending applied. The word reflects the historical North Germanic inflectional system and retains the thorn letter þ (thorn) in modern Icelandic orthography, a feature that distinguishes it from English and many other languages.

See also: Icelandic language, demonstratives, Old Norse.