Compare I opened the door and the door opened. The first has an agent doing the opening; the second describes the same change of state with no agent at all — the door just came open. Linguists call this the causative–inchoative alternation, and every language has to decide how to mark its two sides. English mostly uses the same verb for both (open / open, break / break, boil / boil). Norwegian has three strategies, and choosing among them — bare labile verb, anticausative seg, -s middle, or bli + adjective — is a genuine C1 subtlety, because some verbs allow the bare intransitive and others require the seg. This page sorts them out, and draws the line that English speakers most need: the anticausative seg ("by itself") is not the same as a genuine reflexive ("to oneself"). For the reflexive proper, see verbs/reflexive-seg; for the -s middle in general, verbs/middle-voice-s.
Labile verbs: one verb, both valencies
Many Norwegian verbs are labile: the same form works transitively (with an agent and object) and intransitively (the thing undergoing the change is the subject), with no extra marking. These are the easy ones — they behave just like their English counterparts.
Jeg koker vann til te.
I'm boiling water for tea. (transitive — I'm the agent)
Vannet koker — slå av plata!
The water's boiling — turn off the hob! (intransitive — no agent, the water just boils)
The same verb koke covers both. Likewise smelte (melt), brenne (burn), tørke (dry), velte (tip over):
Sola smelter snøen.
The sun is melting the snow. (transitive)
Snøen smelter fort i sola.
The snow is melting fast in the sun. (intransitive — anticausative, no seg needed)
Han brente brevet.
He burned the letter. (transitive)
Maten brenner — kjenner du lukta?
The food's burning — can you smell it? (intransitive)
The anticausative seg: change of state "by itself"
Other verbs do not alternate freely. To express the agentless change of state, they require seg — the so-called anticausative or inchoative seg. Åpne is the classic case: transitively you say åpne noe, but for "come open on its own" you add seg.
Vakten åpnet porten.
The guard opened the gate. (transitive — agent)
Døra åpnet seg sakte, helt av seg selv.
The door opened slowly, all by itself. (anticausative 'seg' — no one opened it)
The seg here does not mean the door opened itself in any agentive sense — there is no agent. It marks that the change happened spontaneously, without an external cause. The same pattern governs a whole class of "process" verbs:
- lukke seg — close (by itself)
- bevege seg — move
- forandre / endre seg — change
- utvikle seg — develop
- spre seg — spread
- samle seg — gather
- danne seg — form
Såret lukket seg etter noen dager.
The wound closed up after a few days. ('lukke seg' — spontaneous)
Situasjonen utviklet seg raskt og uforutsigbart.
The situation developed rapidly and unpredictably. ('utvikle seg')
Ryktet spredte seg som ild i tørt gress.
The rumour spread like wildfire (lit. fire in dry grass). ('spre seg')
En stor folkemengde samlet seg foran rådhuset.
A large crowd gathered in front of the town hall. ('samle seg')
Why seg for these and bare for koke? There is no fully predictive rule — it is partly lexical, something you learn verb by verb. But a useful heuristic: verbs of internal process and gradual change of configuration (open, close, move, develop, spread, gather, form) tend to take seg, while verbs of physical state change through energy (boil, melt, burn, dry) tend to be bare labile. Expect exceptions; treat the seg as part of the verb's entry.
Anticausative seg vs genuine reflexive: the line that matters
This is the distinction English speakers most need, because both use seg yet mean entirely different things. A genuine reflexive has an agent acting on itself — the subject both does and undergoes the action. An anticausative has no agent — the subject only undergoes it.
| Genuine reflexive | Anticausative seg | |
|---|---|---|
| Agent? | yes — subject acts | no — happens spontaneously |
| Meaning of seg | "oneself" (object = subject) | "by itself" (no real object) |
| 'selv' possible? | yes (vasker seg selv) | no (*døra åpner seg selv ≠ same) |
| Example | Hun vasker seg. | Døra åpner seg. |
Barnet vasker seg selv nå — det er blitt så stort.
The child washes itself now — it's grown so big. (genuine reflexive: an agent, 'selv' fits)
Døra åpner seg automatisk når du går mot den.
The door opens automatically as you approach it. (anticausative: no agent, the door just opens)
The test: can you add selv ("self") and keep the meaning? Hun vasker seg selv is fine — there's a real agent washing a real object. Døra åpner seg selv shifts the meaning toward "the door opens itself" as if it were animate, which is not the plain anticausative. So if selv sounds odd, you have an anticausative, not a reflexive.
Body-posture seg: a special inchoative
A small but high-frequency group uses seg for changes of bodily posture — sette seg (sit down), legge seg (lie down), reise seg (stand up), snu seg (turn round). These straddle the categories: there is a mild agent (you do move your body), but the seg marks the change of position the body undergoes, paralleling the inchoative. Crucially, Norwegian distinguishes the posture-change (with seg) from the static posture (a separate positional verb).
Sett deg, så snakker vi om det.
Sit down, and we'll talk about it. ('sette seg' = change to a sitting position)
Hun reiste seg og forlot rommet uten et ord.
She stood up and left the room without a word. ('reise seg' = rise to standing)
Jeg legger meg tidlig i kveld.
I'm going to bed early tonight. ('legge seg' = lie down / turn in)
Contrast these change-of-state verbs with the static positional verbs that describe being in the position — sitte, ligge, stå — which take no seg. Jeg setter meg (I sit down) vs jeg sitter (I am sitting); for that whole contrast see verbs/positional-verbs.
The -s middle: agentless and formal
A subset of anticausatives can also be expressed with the -s ending — the middle/passive marker — which strips the agent entirely and reads as more formal, written, or generic. Where seg foregrounds spontaneity, the -s form is impersonal and often institutional.
Dørene åpnes klokka ti. (formal/written, e.g. a sign)
The doors open at ten. (impersonal -s — typical of notices and announcements)
Saken avgjøres av styret neste uke. (formal)
The matter will be decided by the board next week. (-s middle/passive, formal)
Note the register split: a shop sign says dørene åpnes kl. 10, but you would describe a door blowing open as døra åpnet seg. The -s leans toward scheduled, official, agent-suppressed events; seg toward spontaneous physical happenings. For the full middle-voice -s, see verbs/middle-voice-s.
bli + adjective: the gradual inchoative
Finally, Norwegian expresses becoming — entering a state described by an adjective — with bli + adjective. This is the inchoative of states: where være stor is be big, bli stor is grow / get big.
Barna blir så store så fort.
The kids grow so big so fast. ('bli stor' = grow/become big)
Det ble mørkt før vi kom fram.
It got dark before we arrived. ('bli mørk' = get dark)
Han ble sint da han hørte nyheten.
He got angry when he heard the news. ('bli sint' = become angry)
This is why English speakers must not reach for være here: være sint = be angry (a state), but bli sint = get angry (entering the state). The bli/være split is the adjectival face of the inchoative/stative contrast — see choosing/vaere-vs-bli.
Common Mistakes
Adding seg to a labile verb that doesn't want it. Over-marking the inchoative.
❌ Snøen smelter seg i sola.
Wrong — 'smelte' is labile; the intransitive needs no 'seg': 'Snøen smelter i sola'.
✅ Snøen smelter i sola.
The snow is melting in the sun.
Dropping seg from a verb that requires it. Under-marking the anticausative.
❌ Døra åpnet plutselig. (meaning: came open on its own)
Incomplete — 'åpne' needs 'seg' for the agentless reading: 'Døra åpnet seg plutselig'.
✅ Døra åpnet seg plutselig.
The door suddenly opened (by itself).
Confusing anticausative seg with a reflexive (adding selv). Treating "come open" as "open itself."
❌ Vinduet åpner seg selv om natta. (meaning: the window opens on its own)
The 'selv' implies the window is an agent opening itself; for the plain spontaneous reading, drop it: 'Vinduet åpner seg om natta'.
✅ Vinduet åpner seg om natta.
The window comes open at night (by itself).
Using være instead of bli for becoming. Stative where inchoative is meant.
❌ Det er mørkt klokka fire om vinteren. (meaning: it gets dark)
That states a fact ('it is dark at four'); for the change use 'bli': 'Det blir mørkt klokka fire'.
✅ Det blir mørkt klokka fire om vinteren.
It gets dark at four in winter.
Confusing posture-change seg with the static positional verb. Sette seg vs sitte.
❌ Jeg sitter ved siden av deg. (meaning: I'll sit down next to you, now)
'sitter' = 'am sitting' (state); to sit DOWN use 'sette seg': 'Jeg setter meg ved siden av deg'.
✅ Jeg setter meg ved siden av deg.
I'll sit down next to you.
Key Takeaways
- The causative–inchoative alternation is marked three ways in Norwegian: labile (bare) verbs (vannet koker), anticausative seg (døra åpner seg), and the -s middle (dørene åpnes, formal).
- Labile verbs (koke, smelte, brenne, tørke) need no marking intransitively; process verbs (åpne, lukke, bevege, utvikle, spre, samle) require seg — this is partly lexical, learned per verb.
- The anticausative seg ("by itself," no agent) is not a genuine reflexive ("oneself," real agent) — the selv-test separates them (it fits vaske seg, not åpne seg).
- Posture-change verbs (sette/legge/reise seg) take seg; the static counterparts (sitte, ligge, stå) don't.
- bli + adjective is the inchoative of states (bli stor = grow), distinct from stative være.
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Start learning Norwegian→Related Topics
- Reflexive Verbs and segA2 — How Norwegian reflexive verbs work — the meg/deg/seg paradigm, true reflexives like vaske seg, and the many inherently reflexive verbs (glede seg, føle seg) English has no equivalent for.
- Middle and Reciprocal -s Verbs: møtes, ses, slåss, minnesB2 — The -s form that is neither active nor passive — reciprocal verbs (møtes, ses, slåss) where -s means 'each other', plus middle-voice verbs like minnes, and how they differ from the passive.
- Positional and Posture Verbs: ligge, sitte, stå, hengeB1 — Where English says an object 'is' somewhere, Norwegian picks a posture verb that encodes the object's orientation — ligge (lying flat), stå (standing upright), sitte (stuck/seated), henge (hanging) — and their transitive partners legge, sette, stille, henge.
- The bli-PassiveB1 — How to form the periphrastic bli + past participle passive (ble åpnet, blir valgt, har blitt bygd) and why it — not the s-passive — is the default for specific events.
- være vs bli: Be vs BecomeA2 — Use være for a state that already holds and bli for any change of state, future state, or passive — the single most useful copula distinction in Norwegian.