rísa

rísa ("to rise") is a strong Class-1 verb running on the familiar í – ei – i – i series (rís, reis, risu, risið) — the same template as bíta, skína and líða. But the thing that actually matters about rísa is not its vowels; it is its valency. rísa is strictly intransitive: the sun rises, prices rise, a person rises (gets up) — there is no object. To say someone raises or erects something — a building, a flag, a tent — you need its transitive causative partner reisa ("raise, erect"), which is a weak verb (reisti). English collapses both onto "rise/raise," but the pair is so easy to confuse that the wrong verb plus the wrong case is the signature learner error. This page gives the full paradigm and keeps rísa and reisa firmly apart.

Conjugation

Class: strong, Class 1 (the í – ei – i – i series). Auxiliary: hafa — ég hef risið "I have risen." The stem vowel is the only moving part: present í (rís), preterite singular ei (reis), preterite plural short i (risu), supine short i (risið).

The í – ei – i – i series

rísa is a clean Class-1 verb, so it follows bíta exactly. The present keeps the infinitive's í (rís). The preterite singular becomes the diphthong ei (reis). The preterite plural and the supine drop to short i (risu, risið). Watch the wide gap between singular reis and plural risu — ei versus short i — which is the most error-prone spot in the whole paradigm.

rísa is intransitive — there is no object

This is the load-bearing point. rísa describes something coming up under its own steam: the sun rising, dough rising, prices or a river rising, a person getting to their feet. It never takes a direct object. So you cannot rísa a building or rísa a flag — for that you need reisa (below). The common figurative extension is rísa upp "rise up, get up; (figuratively) revolt, rise against," and rísa gegn "rise against."

rísa vs reisa — the causative pair

Here is the pair that English speakers must internalise. rísa (strong, reis) = go up on its own (intransitive). reisa (weak, reisti) = make something go up, i.e. raise, erect, build (transitive, + accusative). They are historically the same root — reisa is literally the causative of rísa — which is exactly why they look alike and mean opposite sides of the same event.

So the building rose is byggingin reis, but they raised the building is þeir reistu bygginguna (accusative object). Mixing them — reisa with no object, or rísa with one — is the giveaway error.

rísa vs standa upp — two ways to 'get up'

For a person leaving a chair, both rísa upp and standa upp mean "get up, stand up," but they differ in register and frequency. standa upp is the everyday, neutral, spoken choice (ég stóð upp og fór). rísa (upp) is a touch more formal, deliberate, or literary — you rise to your feet, rise to speak, rise from the dead (rísa upp frá dauðum). Use standa upp in conversation; reach for rísa when you want the weightier, more elevated tone.

Common Mistakes

The headline error: using rísa transitively. rísa never takes an object; the causative reisa (+ accusative) does.

The sun comes up by itself — intransitive rísa (sólin rís), not reisa.

Regularising to -aði is the standard strong-verb slip. The preterite is reis.

The supine has short i: risið. The ei belongs only to the preterite singular reis.

Key Takeaways

• rísa is strong Class 1, series í – ei – i – i: rís (pres.), reis / risu (past sg./pl.), risið (supine), risinn (participle).
• It is intransitive — the sun, dough, prices, a person all rise on their own; there is no object. Common: rísa upp "get up; rise up / revolt."
• Its transitive twin is the weak causative reisa (reisti, + accusative) = "raise, erect, build." Byggingin reis "the building went up" vs þeir reistu bygginguna "they built the building."
• For a person getting out of a chair, standa upp is the everyday word; rísa (upp) is more formal/literary (rise to speak, rísa upp frá dauðum).
• Watch the present -s stem (ég/þú/hann rís, no -ur), the reis vs risu split, and the short-i supine risið. Auxiliary is hafa: ég hef risið.