sá, sú, það as Pronouns

The little word sá and its forms sú (feminine) and það (neuter) do two quite different jobs in Icelandic. As a determiner it sits in front of a noun — sá maður "that man", sú kona "that woman" — and that use is covered on the Demonstratives page. This page is about the other job: sá / sú / það standing alone, as a full pronoun, with no noun behind it. Pronominal sá sem is the standard Icelandic way to say "the one who / he who", þeir sem is "those who", and það is the everyday neuter pronoun "it / that" — the word you reach for to point at a whole situation, an idea, or an unnamed thing. English splits this work across he who, the one that, those who, it, and that; Icelandic funnels almost all of it through one irregular paradigm.

One paradigm, two jobs

Whether sá stands before a noun or alone, it declines exactly the same way. The forms are old and irregular — you cannot derive them from a stem by rule — so the table is worth memorising as a block.

Notice the spelling traps the orthography rewards you for getting right: the masculine accusative is þann with a double n; the genitive singular (masc. and neut.) is þess with a double s; the feminine has the doubled-r shapes þeirri (dat.) and þeirrar (gen.). The word always begins with þ — sá, sú, það, þann, þeim, þess — never with d or th. And the plural nominative/accusative neuter is þau, not þeir.

sá sem — "the one who / he who"

The headline use is sá sem (and sú sem, þeir sem, þær sem, þau sem): a demonstrative that points forward to a relative clause introduced by sem. Literally it is "that-one who…", and it is the normal, idiomatic Icelandic for a headless relative — a relative with no noun to modify. English has the slightly bookish "he who", "the one who", "those who"; Icelandic uses sá sem in completely ordinary speech.

The demonstrative carries the gender, number and case demanded by the main clause, while sem (which never inflects) opens the relative. So in Ég treysti þeim sem segja satt — "I trust those who tell the truth" — the verb treysta governs the dative, and that dative lands on the demonstrative: þeim sem, not þeir sem.

This is the single most important pattern on the page. When you want to say "whoever / the one who / those who" and there is no noun, the default is sá / sú / það / þeir … sem, with the demonstrative taking its case from the outer clause.

það — the all-purpose neuter pronoun

Pronominal það is the workhorse "it / that". It refers back to things, to the neuter, and — crucially — to whole clauses and situations. When English says "That's true", "I knew it", "Is that so?", or points vaguely at a state of affairs, Icelandic reaches for það.

Because það is the neuter, it is the default antecedent whenever there is no specific noun to agree with — a clause, an action, an abstract "thing". This is why "It's raining", "It's nice that you came", and "I find that strange" all use það even though there is no neuter noun in sight. (The purely grammatical, meaningless "dummy" það that merely fills the first slot of a sentence — Það var einu sinni… "Once upon a time…" — is a related but separate topic, treated on the Dummy það page.)

það in oblique cases

Like every demonstrative, það changes shape in the other cases, and learners often forget this because English it never moves. After a preposition or a case-governing verb, það becomes því (dat.) or þess (gen.).

The fixed phrase vegna þess (að) — literally "because of that (that)" — is the most common Icelandic word for "because" in writing, and it is built on the genitive þess. Seeing þess here, not það, is the kind of detail that separates careful learners from the rest.

sá / það vs the personal pronouns hann / hún / það

Here is where English habits steer learners wrong. In English you say "He who hesitates is lost" only in proverbs; in normal speech you would more often restructure. Icelandic, by contrast, strongly prefers the demonstrative sá / sú over the personal pronoun hann / hún when a relative clause follows and there is no antecedent noun.

So "the one who broke the window" is naturally sá sem braut rúðuna, not hann sem braut rúðuna. Using hann sem is not flatly ungrammatical, but it sounds off — as if you were pointing at a specific known male rather than introducing "whoever it was". The demonstrative is the neutral, idiomatic choice for headless relatives.

Conversely, when you are referring to a definite, already-mentioned person, you use the personal pronoun: Ég talaði við Jón. Hann var þreyttur. "I talked to Jón. He was tired." There hann is right and sá would be wrong. The division of labour is: personal pronoun for known referents already in play; demonstrative sá / sú for "the one(s) who…" introduced by a relative. The choice between það and hann/hún when referring to people and things has its own dedicated page.

Common Mistakes

English "he who / the one who" tempts learners into hann sem. The idiomatic Icelandic is sá sem (and sú / þeir / þær / þau sem).

The demonstrative in sá … sem takes its case from the main clause. Don't leave it in the nominative just because sem doesn't inflect.

Treating það as invariant (the way English it never changes) is a classic transfer error. After prepositions and case-governing verbs it becomes því (dat.) or þess (gen.).

"Because" is vegna þess að, built on genitive þess. The first það must be in the genitive; only the weather það stays as það.

Don't freeze on þeir sem. Match the demonstrative to the gender and number of the people meant: þeir (masc.), þær (fem.), þau (mixed/neuter).

Key Takeaways

• sá / sú / það decline through one irregular paradigm; the nominative starts with s (sá, sú, það) but every other cell starts with þ (þann, þeim, því, þess, þeir, þær, þau).
• sá sem / þeir sem is the standard, idiomatic "the one who / those who" — preferred over hann sem / hún sem for headless relatives.
• The demonstrative takes its case from the main clause (treysti þeim sem…), while sem never inflects.
• það is the go-to neuter pronoun for things and especially for whole clauses and situations ("That's true", "I find it strange that…").
• það is not invariant: after prepositions and case-governing verbs it becomes því (dat.) or þess (gen.) — as in áhuga á því, vegna þess að.