Demonstratives: þessi and sá

Icelandic has two demonstratives for pointing at things: þessi for what is near — "this" — and sá for what is farther off or already under discussion — "that, the (one)." Both decline fully for gender, number and case, so unlike English "this/that" (which only changes for number) they reshape themselves to match the noun. Two facts make this page worth real attention: sá is ancient and irregular, and its neuter form is the famous little word það that simultaneously means "that," serves as the pronoun "it," and acts as the dummy subject "there/it." This page covers þessi and sá as determiners standing in front of a noun; the suffixed article and the standalone pronoun sá have their own pages.

þessi: "this" (proximal)

Þessi points at what is close — in space, in time, or in the conversation. Its declension is its own (it is not built like an adjective), and the form you must lock in first is the nominative singular across the genders: þessi (masc.), þessi (fem.), þetta (neut.).

Two forms deserve a flag. The masculine accusative singular is þennan — irregular, not the \þessan you might expect from the stem. And the feminine dative singular is *þessari (with the doubled-looking -ssari), which learners often clip to \þessi. When you point at a feminine noun in the dative, it is þessari*, full stop.

The third example shows the declension doing its job: hús is neuter and the preposition í (location) takes the dative, so "this" becomes the neuter dative þessu — í þessu húsi. The demonstrative tracks both the gender and the case of its noun.

sá: "that, the one" — ancient and irregular

Sá is one of the oldest words in the language, and its paradigm is gloriously irregular: the singular looks built from two different stems (s- in the nominative, þ- everywhere else), and the plural is identical to the third-person plural pronoun and to the demonstrative endings of sá's neighbours.

Look at the nominative singular: sá (masc.), sú (fem.), það (neut.) — these three forms have no resemblance to one another and simply must be memorised. The masculine sá and feminine sú differ only by the vowel and the accent, so guard those two characters carefully: sá has the acute on a, sú the acute on u.

Sá is more than a pointer; it is anaphoric — it reaches back to something already mentioned, often introducing a relative clause: sá sem "the one who," þeir sem "those who." That pronominal life is covered on its own page; here, note that as a determiner before a noun it means "that (specific, known) one."

það — one spelling, three jobs

The neuter of sá is það, and it is the busiest word in Icelandic, because it wears three hats that competitors' grammars rarely connect:

So when you meet það, decide which job it is doing. As a demonstrative it modifies or stands for a neuter noun; as a pronoun it replaces a neuter noun ("it"); and as the dummy subject it fills the subject slot when no real subject exists ("it's raining," "there is…"). The dummy-subject use has its own detailed page. The reason all three coincide is historical: the neuter demonstrative bleached into the all-purpose neuter pronoun and then into the placeholder — but the word is the same.

þetta and það as sentence openers

A point of high frequency for beginners: to say "this is …" or "that is …" when introducing or identifying something, Icelandic opens with the neuter demonstrative regardless of the gender of what follows. Þetta er bók ("this is a book") uses neuter þetta even though bók is feminine; það var gaman ("that was fun") uses neuter það. The neuter is the default for "this/that" pointing at an unidentified or whole-situation referent.

Demonstratives make the adjective weak

When a demonstrative stands before an adjective + noun, it forces the adjective into its weak declension — the same set of endings the suffixed article triggers. So "this old man" is þessi *gamli maður (weak *gamli), not þessi *gamall maður (strong *gamall). The demonstrative has already "definitised" the phrase, so the adjective signals that with its weak form. The full weak paradigm is on the adjectives page; the rule to fix here is simply: demonstrative → weak adjective.

Common Mistakes

The biggest English-transfer error is treating þetta/það as an invariant "this/that." They are only the nominative/accusative neuter forms; in other cases the demonstrative declines (þessu, því, þeirri…).

After þessi or sá the adjective goes weak. Using the strong form (the dictionary form) is a frequent slip because the strong form is the one learners memorise first.

Sá / sú / það must match the noun's gender. Defaulting to masculine sá for every "that" ignores the agreement.

The masculine accusative þennan is irregular and trips up learners who build it by analogy. There is no \þessan*.

For "this is / that is" identifications, lead with neuter þetta / það even when the predicate noun is feminine or masculine.

Key Takeaways

• Two demonstratives: þessi "this" (near) and sá "that / the one" (far / already-mentioned), both fully declined for gender, number and case.
• Nominative singulars to memorise: þessi / þessi / þetta and the irregular sá / sú / það.
• það does three jobs — neuter of sá ("that"), the pronoun "it," and the dummy subject "there/it" — one spelling, three functions (each with links above).
• "This is / these are" opens with the neuter þetta (and það for "that was…") whatever the gender of what follows.
• A demonstrative makes the following adjective weak: þessi gamli maður, sú litla stúlka.
• Watch the traps: masc. acc. þennan, fem. dat. þessari; and sá (masc.) vs sú (fem.).