Dormir

Dormir means to sleep (and, by extension, to fall asleep). It is an -ir verb with a stem change: the o of the stem turns into u wherever the stress would otherwise fall on it, which in practice means the eu form of the present (durmo) and the entire present subjunctive (durma, durmas, durma...). Everywhere else the o stays put. This o→u alternation is shared by a small family of -ir verbs (dormir, tossir, engolir, cobrir, descobrir), so learning dormir well unlocks the whole pattern. English has no equivalent — our verbs don't shift vowels by stress — so this is something to drill until it feels automatic.

Why the vowel changes

The change is driven by stress, not by meaning. In the eu form durmo and the present subjunctive durma, the stress falls on the stem vowel, and that stressed mid vowel o raises to the high vowel u. In dormimos the stress moves to the ending, so the vowel stays o. This is a remnant of how Latin vowels behaved under stress, and the same logic explains why subir gives subo but sobe, just in the opposite direction. You don't have to know the history — but knowing it's about where the stress lands tells you exactly which forms change.

Presente do indicativo

Only durmo changes. The trap for learners is producing dormo — natural by analogy, but wrong. Everyone else keeps the o.

Pretérito perfeito

Completely regular — the stem stays dorm- and the o does not change.

Note that dormimos (nós) is the same in the present and the preterite — context tells you whether it means "we sleep" or "we slept."

Pretérito imperfeito

Regular, with -ir/-er imperfect -ia endings; the o stays.

Futuro do presente & futuro do pretérito (conditional)

Both built on the full infinitive dormir-; no vowel change.

In everyday speech, the simple future is usually replaced by ir + infinitive: vou dormir rather than dormirei. (informal)

Presente do subjuntivo

This is where the o→u change spreads to every person, because the subjunctive is built on the eu stem durm-.

This catches learners off guard: even durmamos ("that we sleep") takes the u, unlike the indicative dormimos.

Imperfeito & futuro do subjuntivo

Both are built on the regular preterite stem dorm- — so, no u here.

Imperativo

The você imperative comes from the subjunctive, so it takes the u: durma. The tu affirmative comes from the indicative, so it keeps the o: dorme. This split is the single trickiest thing about the verb.

Non-finite forms

All regular — the o stays in every non-finite form.

Meaning, collocations, and register

The core sense is to sleep. Brazilian Portuguese also uses dormir for to fall asleep ("o bebê dormiu" = "the baby fell asleep / went to sleep"), where English forces a distinction. Some useful collocations:

• dormir cedo / tarde — to go to bed early / late
• dormir feito uma pedra — to sleep like a log ("like a rock")
• dormir no ponto — to drop the ball, to miss your chance (literally "to fall asleep at the bus stop") (informal)
• pegar no sono — to fall asleep / drift off (the moment of falling asleep)

Common Mistakes

Key Takeaways

• Dormir is an -ir verb with an o→u stem change driven by stress.
• The u appears in durmo (eu, present) and the entire present subjunctive (durma, durmas, durma, durmamos, durmam) — plus the você imperative durma.
• Everywhere else (dorme, dormimos, dormiu, dormia, dormir) the o stays.
• Dormir covers both "sleep" and "fall asleep"; use pegar no sono for the moment of drifting off.
• The same o→u pattern shows up in tossir, engolir, cobrir, and descobrir.