A relative clause adds information about a noun: the man that I saw, the woman who lives here, the house that we bought. Icelandic builds these with one short, unchanging word — sem — placed right after the noun it describes. What makes Icelandic relative clauses worth a careful page is not the marker (it never changes) but the machinery inside the clause: the relativised role leaves a gap, the gap's case is recovered from inside the clause, prepositions are stranded at the end, and — the feature competitors skip — possessive and oblique relatives often plant a resumptive pronoun in the gap, a strategy English handles with "whose" but Icelandic does out in the open.
sem follows the noun and never inflects
The relative clause comes after its head noun, and sem opens it. Sem is invariant: it does not change for gender, number, or case. One word covers English who, whom, which, and that.
| Head noun | Relative clause | English |
|---|---|---|
| maðurinn | sem ég sá | the man that I saw |
| konan | sem býr hér | the woman who lives here |
| húsið | sem við keyptum | the house that we bought |
Konan sem býr hér er læknir.
The woman who lives here is a doctor. (subject relative — sem followed directly by the verb)
Maðurinn sem ég sá í gær var frændi minn.
The man that I saw yesterday was my cousin. (object relative)
In formal or literary writing you may also meet er as a relativiser (maðurinn er ég sá — "the man whom I saw"). It is the same function in an older register; in everyday Icelandic, use sem.
Subordinate word order inside the clause
A relative clause is a subordinate clause, so the V2 inversion of main clauses does not apply inside it. The subject stays before the verb, and any sentence adverb (ekki, alltaf) comes before the finite verb, not after it. This is a key difference from the main clause.
| Main clause (V2) | Relative clause (subordinate) |
|---|---|
| Ég sá hann ekki. | maðurinn sem ég sá ekki |
| Hún kemur alltaf. | konan sem alltaf kemur |
Þetta er konan sem ekki kemur oft.
This is the woman who doesn't come often. (subordinate order — the sentence adverb ekki can sit before the finite verb kemur; no V2 inversion)
Maðurinn sem ég sá ekki var samt þarna.
The man that I didn't see was there all the same. (subject ég stays before the verb sá — no inversion inside the clause)
The gap and its case
Here is the engine of the whole system. When you relativise a role — subject, object, whatever — that role is left empty inside the clause: a gap. Because sem itself carries no case, the gap silently takes whatever case the verb or preposition inside the clause would have assigned to the missing noun. You recover the case by asking: what role does the head noun play inside the relative clause?
- Subject relative: the gap is the subject, so it would be nominative. konan sem býr hér — konan is the subject of býr.
- Object relative: the gap is the object, so it takes the object case. kakan sem hún bakaði — kakan is the accusative object of bakaði.
Kakan sem hún bakaði var himnesk.
The cake that she baked was heavenly. (object relative — the gap is the accusative object of bakaði)
Strákurinn sem hjálpaði mér heitir Ari.
The boy who helped me is called Ari. (subject relative — gap is the nominative subject of hjálpaði)
Stranded prepositions: the preposition stays at the end
When the relativised noun is the object of a preposition, Icelandic does not move the preposition up next to sem. It leaves it stranded at the end of the clause, exactly where it would sit in a plain sentence. Compare Ég bý í húsinu ("I live in the house") with the relative húsið sem ég bý í — the í stays put at the end.
| Plain sentence | Relative clause |
|---|---|
| Ég bý í húsinu. | húsið sem ég bý í |
| Ég talaði við manninn. | maðurinn sem ég talaði við |
| Hún beið eftir strætó. | strætóinn sem hún beið eftir |
Þetta er húsið sem ég bý í.
This is the house that I live in. (stranded preposition í at the end)
Maðurinn sem ég talaði við var mjög vingjarnlegur.
The man that I spoke to was very friendly. (stranded við)
The stranded preposition still governs the case of the gap, even though there is no visible noun for it to govern — í would take the dative, við the accusative, and the system "knows" this even with the slot empty. English does the same thing colloquially ("the house I live in"), so stranding should feel natural; what feels wrong to English speakers is trying to front the preposition next to sem (the house *in sem I live*), which Icelandic never does.
Possessive and oblique relatives: the resumptive pronoun
This is the part most guides leave out, and it is where Icelandic genuinely differs from English. English has a dedicated possessive relative pronoun, whose ("the man whose car broke down"). Icelandic has no such word — sem cannot inflect to mean "whose." Instead, Icelandic keeps sem and plants a resumptive pronoun inside the clause: a real, visible pronoun that fills the role and carries the case the gap could not. The clause literally says "the man that his car broke down."
| Icelandic | Literal | Idiomatic English |
|---|---|---|
| maðurinn sem bíllinn hans bilaði | the man that the car of-his broke down | the man whose car broke down |
| konan sem maðurinn hennar dó | the woman that the husband of-hers died | the woman whose husband died |
Maðurinn sem bíllinn hans bilaði þurfti að taka strætó.
The man whose car broke down had to take the bus. (resumptive hans = 'his' inside the clause)
Þetta er konan sem dóttir hennar vann keppnina.
This is the woman whose daughter won the competition. (resumptive hennar = 'her')
The resumptive hans / hennar is not optional padding — it is required, because there is no other way to express possession across the relative boundary. English suppresses the pronoun and uses "whose"; Icelandic keeps the pronoun and uses ordinary sem. Resumptives also appear in some heavier oblique relatives where the gap would be hard to track:
Maðurinn sem ég sá bílinn hans var ekki heima.
The man whose car I saw wasn't home. (resumptive hans inside; the gap relation is possessive)
Once you see that Icelandic simply re-uses a normal possessive pronoun inside the clause, "whose" stops being a puzzle: you say "the man that... his car..." and let sem do the joining.
Dropping sem colloquially
In casual speech, sem can be omitted in some object relatives, much as English drops "that" in "the book I read." This is informal; in writing, keep sem.
Bókin (sem) ég las í gær var spennandi.
The book (that) I read yesterday was exciting. (sem droppable in object relatives, informal)
You cannot drop sem in a subject relative, though — konan býr hér without sem would just be a main clause ("the woman lives here"), losing the relative link. The omission is only available when sem is followed by a subject, not when sem is itself standing in for the subject.
Restrictive vs non-restrictive
A restrictive relative clause narrows down which noun you mean and takes no comma: maðurinn sem ég sá ("the man that I saw" — specifying which man). A non-restrictive clause adds a side comment about an already-identified noun and is set off with a comma: Jón, sem ég þekki vel, ... ("Jón, whom I know well, ..."). The marker is still sem; only the comma and the function differ.
Systir mín, sem býr í Noregi, kemur í heimsókn í sumar.
My sister, who lives in Norway, is visiting this summer. (non-restrictive — comma; she's already identified)
Common Mistakes
❌ Maðurinn semsem ég sá... / Maðurinn semur ég sá.
Incorrect — sem never inflects or doubles; it is always just sem.
✅ Maðurinn sem ég sá var frændi minn.
The man that I saw was my cousin.
Sem is invariant. There is no semur, no agreement, no case form — the temptation to "decline" it like other Icelandic words is exactly what to resist.
❌ Húsið í sem ég bý er gamalt.
Incorrect — the preposition strands at the end, it does not front to sem: sem ég bý í.
✅ Húsið sem ég bý í er gamalt.
The house that I live in is old.
Do not pull the preposition up next to sem. Leave it stranded at the end of the clause: sem ég bý *í*.
❌ Maðurinn sem bíll bilaði var reiður.
Incomplete — a possessive relative needs the resumptive pronoun: bíllinn hans.
✅ Maðurinn sem bíllinn hans bilaði var reiður.
The man whose car broke down was angry.
There is no word for "whose." Express possession with a resumptive pronoun inside the clause — bíllinn hans ("his car") — and keep plain sem.
❌ Konan hver býr hér er læknir.
Incorrect — hver is the question word 'who/which', not a relativiser; use sem.
✅ Konan sem býr hér er læknir.
The woman who lives here is a doctor.
Do not borrow the interrogative hver ("who?") as a relative pronoun the way English uses "who." Icelandic relatives use sem (or formal er), never hver.
❌ Kakan sem hún bakaði hana var góð.
Incorrect — a plain object relative leaves a gap, no resumptive: ...sem hún bakaði.
✅ Kakan sem hún bakaði var góð.
The cake that she baked was good.
A straightforward object relative uses a gap, not a resumptive — don't add an extra hana ("it"). Resumptives are for possessive and heavier oblique relatives, not simple objects.
Key Takeaways
- sem follows the head noun and never inflects — one word for who, whom, which, that; formal/literary er is the alternative.
- Inside the clause the word order is subordinate (no V2 inversion; sentence adverbs precede the finite verb).
- The relativised role leaves a gap whose case is recovered from inside the clause (subject → nominative, object → object case).
- Prepositions strand at the end and still govern the gap's case: húsið sem ég bý *í*.
- Possessive relatives have no "whose" — they use a resumptive pronoun: maðurinn sem bíllinn *hans bilaði*.
- Sem can be dropped in some object relatives (informal), but never in subject relatives.
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- The Relative Clause Marker sem (and er)A2 — The invariant Icelandic relativizer sem — the single word that covers English who, which and that for every gender, number and case — how the relativised noun's case is recovered from the gap, how prepositions strand, and the literary alternative er.