þvo ("to wash") is one of the small, ancient verbs that every learner uses on day one and gets wrong for months, because its stem refuses to stay still. You wash with þvæ in the present, washed with þvoði in the past, and have washed with þvegið in the supine — three different shapes of the same root. It is a contract verb (the þvo type), a tiny historical class, and there is no shortcut: you memorise the three stems. The reward is a verb you need constantly — for washing your hands, your hair, the dishes, and the laundry.
Conjugation
Class: strong / contract verb (the þvo type — historically a class-6 strong verb that contracted). Auxiliary: hafa — ég hef þvegið "I have washed." The three stem shapes are þvæ- (present singular), þvo- (present plural and the -ði past), and þveg- (supine and participle).
| Principal parts | |
|---|---|
| Infinitive | að þvo |
| 1sg present | þvæ |
| 1sg past | þvoði |
| 3pl past | þvoðu |
| Supine | þvegið |
| Person | Present (nútíð) | Past (þátíð) |
|---|---|---|
| ég | þvæ | þvoði |
| þú | þværð | þvoðir |
| hann / hún / það | þvær | þvoði |
| við | þvoum | þvoðum |
| þið | þvoið | þvoðuð |
| þeir / þær / þau | þvo | þvoðu |
| Person | Present subjunctive | Past subjunctive |
|---|---|---|
| ég | þvoi | þvæði |
| þú | þvoir | þvæðir |
| hann / hún / það | þvoi | þvæði |
| við | þvoum | þvæðum |
| þið | þvoið | þvæðuð |
| þeir / þær / þau | þvoi | þvæðu |
| Non-finite & imperative | |
|---|---|
| Imperative (þú) | þvoðu! |
| Imperative (þið) | þvoið! |
| Supine | þvegið |
| Past participle (m/f/n) | þveginn / þvegin / þvegið |
| Middle voice (miðmynd) | þvost — "to get washed / be washed" |
þvo + accusative — wash a thing
In its plain transitive use, þvo takes a direct object in the accusative: þvo bílinn "wash the car," þvo gluggana "wash the windows," þvo hárið "wash one's hair."
Ég þvæ hárið á mér á hverjum degi.
I wash my hair every day.
Hún þvoði alla diskana eftir matinn.
She washed all the dishes after the meal.
þvo sér — "wash oneself" (+ dative reflexive)
To say you wash yourself, Icelandic uses þvo sér, where the reflexive is in the dative (sér, mér, þér), not the accusative. This is the same dative-reflexive pattern as bursta sér tennurnar "brush one's teeth." The body part, if mentioned, is the accusative object, and the dative reflexive marks "to/for oneself."
Þvoðu þér um hendurnar áður en þú borðar!
Wash your hands before you eat!
Hann þvær sér alltaf í framan á morgnana.
He always washes his face in the mornings.
Note þvo sér um hendurnar — literally "wash to-oneself about the hands." The fixed preposition um + the body part is the idiomatic way to say "wash one's hands."
þvo þvott — "do the laundry"
The set phrase þvo þvott ("wash laundry") is how you say "do the washing." þvottur (masculine) is "laundry, the wash"; the verb and noun share the root. The machine is a þvottavél.
Ég þarf að þvo þvott um helgina — það er allt orðið skítugt.
I need to do laundry this weekend — everything's gotten dirty.
The middle voice: þvost
The -st form þvost ("get washed, be washed") makes the thing washed the subject, with no explicit agent — useful for talking about what comes out clean, or for "wash" in the sense of "wash off." A reflexive þvær sér describes a person actively washing; þvost describes the washing happening to something.
Þessi flík þvæst best við þrjátíu gráður.
This garment washes best at thirty degrees.
Common Mistakes
❌ Ég þvo hárið á hverjum degi.
Incorrect — the 1sg present is þvæ, not þvo; say ég þvæ hárið.
✅ Ég þvæ hárið á hverjum degi.
I wash my hair every day.
❌ Þvoðu þig um hendurnar.
Incorrect — the reflexive is dative þér, not accusative þig: þvoðu þér um hendurnar.
✅ Þvoðu þér um hendurnar.
Wash your hands.
❌ Hún þvaði bílinn í gær.
Incorrect — the past keeps the o-stem: þvoði, not þvaði.
✅ Hún þvoði bílinn í gær.
She washed the car yesterday.
❌ Ég hef þvoð alla gluggana.
Incorrect — the supine is þvegið (with g), not þvoð.
✅ Ég hef þvegið alla gluggana.
I have washed all the windows.
Key Takeaways
- þvæ / þvoði / þvoðu / þvegið — an irregular contract verb with three stem shapes: þvæ- (present sg), þvo- (present pl & past), þveg- (supine/participle).
- Present singular has æ (þvæ, þværð, þvær); present plural drops back to the bare stem (þvoum, þvoið, þvo).
- þvo sér = "wash oneself" with a dative reflexive; þvo sér um hendurnar = "wash one's hands."
- þvo þvott = "do the laundry"; the noun is þvottur, the machine þvottavél.
- Middle voice þvost = "get washed / be washed." Auxiliary is hafa: ég hef þvegið.
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