Mood in Relative and Adverbial Clauses

The basic subjunctive comes packaged as a list of triggers — reported speech, conditionals, wishes, certain conjunctions. This page is about something the trigger list never reaches: the mood alternation inside relative and adverbial clauses, where the same surface structure takes the indicative or the subjunctive and the choice encodes whether the thing being talked about actually exists or is merely a type you are describing. This is the relative-clause and temporal-clause face of one principle you already met in the subjunctive in depth: the indicative asserts; the subjunctive does not. (Reported speech has its own page; conditionals have theirs. This page is everything else — relatives, temporals, purpose clauses — and it deliberately leaves those two out.)

The core alternation: specific versus non-specific heads

Take a relative clause modifying a noun. The verb inside it can be indicative or subjunctive, and the difference is whether the head noun points at a specific, real individual or at a non-specific, hypothetical type — "any such X." This is a genuine existential / specificity distinction, and Icelandic marks it in the mood of the relative verb.

When the head is specific — there is an actual man, and you are asserting something about him — the relative verb is indicative:

When the head is non-specific — you are not committed to any such individual existing; you are describing the kind of person you want — the relative verb is subjunctive:

Lay the minimal pair side by side and the principle is undeniable: maðurinn sem kann "the man who (actually) knows" versus manni sem kunni "a man who would know, any such man." The only thing that changed is the mood, and what it changes is whether the referent is asserted to exist.

Why the subjunctive lands here

This is not an arbitrary rule bolted onto relative clauses. It falls straight out of assertion versus non-assertion. To say maðurinn sem kann íslensku is to assert that some actual man knows Icelandic — you are presupposing his existence and vouching for the fact. The indicative is the mood of that commitment. But to say manni sem kunni íslensku under leita að "look for" is to assert nothing about any real man: you are characterising the target of a search, a person who may not exist at all. There is nothing to assert, so the non-asserting mood — the subjunctive — appears.

This is why the matrix predicate matters. Verbs and contexts that create a non-specific, sought-after, or merely possible referent — leita að "look for," þurfa "need," vilja fá "want," óska eftir "request," plus negation and questions over the head — pull the relative into the subjunctive. Verbs that present an actual referent — þekkja "know (someone)," hitta "meet," sjá "see," plain assertion — keep it indicative.

The progression in that triad is the whole lesson: question the existence (Er einhver … kunni), deny the existence (enginn … kunni) → subjunctive; assert the existence (einn … kann) → indicative.

Temporal clauses: the subjunctive is not automatic for the future

Here English speakers over-correct, so be careful. A temporal clause with future reference does not automatically take the subjunctive. After þegar "when," ordinary future events stay indicative — the same indicative you would use for a present or past event.

The reason is exactly the specificity logic again: þegar hann kemur treats his coming as a real, expected event — you are committed to it happening — so it is asserted, hence indicative. Notice that this is the opposite of the Romance pattern (Spanish cuando venga, French would use a future indicative): if you know Spanish, do not transfer the subjunctive into Icelandic þegar-clauses.

The subjunctive does surface in temporal-type clauses when the conjunction itself signals a non-asserted, anticipated-but-uncertain, or "before it has happened" relation — most clearly áður en "before" and þangað til / uns "until," where the event in the clause has not yet occurred and is held open. Even here usage allows the indicative for events treated as certain; the subjunctive marks the event as still merely anticipated.

Purpose clauses: inherently non-asserted

Purpose clauses — til þess að "in order that," svo að "so that" (in its purpose sense) — describe an intended, not-yet-realised goal. The goal is by definition not asserted as fact; it is what you are aiming at. So purpose clauses naturally take the subjunctive.

Contrast a result clause, which states what actually happened and therefore asserts a fact — indicative:

The same svo að string can be a purpose clause (intended → subjunctive) or, with svo as a degree word, a result clause (achieved → indicative). The mood is what disambiguates them. Once more: intended/non-asserted → subjunctive; achieved/asserted → indicative.

Why English gives you no help

English collapses almost all of this. "I'm looking for a man who knows Icelandic" and "This is the man who knows Icelandic" use the identical verb form knows; the only flicker of the distinction is the article — a man (any such) versus the man (specific) — and even that is unreliable. English has no audible mood to transfer, so you have to build the specificity sensor from the ground up. The pay-off is that it is one sensor: the same "is this asserted to exist?" question governs relative clauses, existential and negated heads, and purpose clauses alike, and it is the very same machinery behind belief versus knowledge in complement clauses. Build it once, use it everywhere.

Common Mistakes

This is the signature error: an English speaker, with no mood in their native relative clauses, leaves the relative indicative even when the head is purely hypothetical.

The over-correction of learners who have just discovered the subjunctive — and of Spanish speakers transferring cuando venga. þegar takes the indicative.

The mirror-image over-correction: applying the subjunctive to a relative clause whose head is plainly a real, identified individual.

The subjunctive is the right mood in a purpose clause; the error here is forgetting it still inflects for person and number.

Key Takeaways

• A relative clause takes the subjunctive when its head is non-specific / hypothetical ("any such X") — manni sem kunni — and the indicative when the referent is a specific, real individual — maðurinn sem kann. The mood encodes whether the thing is asserted to exist.
• The trigger is the matrix context: leita að, þurfa, vilja fá, plus negation and questions over the head, create non-specific referents → subjunctive; assertion of an actual referent → indicative.
• Temporal þegar "when"-clauses default to the indicative even for the future (þegar hann kemur). The subjunctive belongs to áður en "before" and þangað til "until," which hold an event open as not-yet-real. Do not transfer Spanish cuando venga.
• Purpose clauses (til þess að, svo að purpose) are inherently non-asserted goals → subjunctive; result clauses (svo … að achieved) assert a fact → indicative.
• English marks the distinction only with a versus the, so build the specificity sensor from scratch — it is the same assertion/non-assertion principle that governs all of Icelandic mood.