Construir

Construir means to build or to construct — a house, a bridge, a relationship, an argument. It looks like a regular -ir verb, and across most tenses it behaves like one, but it hides two separate complications that no English-speaking learner expects. First, the stem constru- ends in a vowel, so wherever an ending also begins with a stressed i you get a hiatus that must be marked with an acute accent: construí, construímos, construíram. Second — and this is the part that surprises everyone — in the present tense the stem vowel u shifts to a stressed ói/o: constrói (he/she builds), constroem (they build). This u→ói alternation is shared by a small family of verbs (destruir, reconstruir, retribuir) and is worth memorizing as a unit.

The u→ói shift in the present

This is the single most important — and most counterintuitive — feature of construir. In the present indicative, when the stress falls on the stem, the u does not stay a u. The first person eu construo keeps the u (because the stress is actually on the o ending, with the u gliding into it), but the você/ele/ela form and the vocês/eles/elas form take a fully stressed ó:

Note the contrast inside the present tense: eu construo (with -u-) but ele constrói (with -ói-). English has nothing like this; the closest analogy is an irregular vowel change like sing → sang, except here it happens within a single tense depending on the person.

The í-accent forms

Wherever the i of the stem carries the stress and stands in a hiatus with the preceding u, it takes an acute accent. This is the same rule you see in cair (caí) and sair (saí):

• Pretérito perfeito: construí (I built), construímos (we built), construíram (they built)
• Pretérito imperfeito: construía, construías, construía, construíamos, construíam
• Particípio: construído

Critically, the third person singular preterite construiu (he/she built) takes no accent — just like caiu and saiu, the iu is a falling diphthong in a single syllable (cons-tru-iu), so there is no hiatus to mark. Compare construí (I built, accented) with construiu (he built, unaccented): the accent is the only signal of who did the building.

Presente do indicativo

The whole irregularity lives here: construo (-u-), constróis and constrói (-ói-), construímos (accented hiatus, no vowel shift because the stress is on the í), and constroem (-o-, the stressed vowel before the -em ending). Brazilians rarely use the tu form constróis; in speech you will overwhelmingly hear você constrói.

Pretérito perfeito

Accents on construí, construíste, construímos, construíram — but construiu takes none. Note also that the nós form construímos is identical in the present and the preterite; context tells you which.

Pretérito imperfeito

Every form is accented, because the i is stressed throughout. No vowel shift here — the u→ói alternation belongs to the present tense only.

Futuro do presente

No accent and no vowel shift — the stress sits on the ending (-rei, -rá, -rão), so the stem stays plain constru-. In everyday speech, Brazilians usually replace this with ir + infinitivo: vou construir (I'm going to build).

Futuro do pretérito (conditional)

Subjunctive

Presente do subjuntivo

The subjunctive is built from the eu construo stem → constru- + a, so there is no vowel shift and no accent: construa, construamos, construam. This catches learners who expect to see constrói leak into the subjunctive — it does not.

Imperfeito do subjuntivo

All accented — built off the preterite stem construí-.

Futuro do subjuntivo

The tu and eles forms (construíres, construírem) carry the accent; bare construir and construirmos do not.

Imperative

The affirmative tu imperative constrói is borrowed from the present indicative constróis minus its -s, which is why it shows the ói shift; the você form construa comes from the subjunctive.

Non-finite forms

Note construindo (no accent — the i glides into the following vowel, no hiatus) versus construído (accent — the i is stressed in hiatus). The same verb shows both behaviors, which is the cleanest illustration of the rule.

The construir family

The u→ói present-tense shift is not unique to construir. Its prefixed and sibling verbs behave identically, so learning one teaches you all:

• destruir → eu destruo, ele destrói, eles destroem (to destroy)
• reconstruir → ele reconstrói, eles reconstroem (to rebuild)
• retribuir → ele retribui, eles retribuem (to reciprocate — note this one keeps a plain i, no ó)

The split is real: construir/destruir/reconstruir take the ói shift, while -buir verbs (atribuir, contribuir, distribuir, retribuir) keep a plain stressed i (ele contribui, eles contribuem). Don't over-generalize the ó.

Source-language note for English speakers

English has separate words — build, construct, erect, develop — that Portuguese mostly funnels into construir. The verb is transitive and takes a direct object with no preposition: construir uma casa (build a house), never "construir de uma casa." Where English says "build on something" (figuratively, build on success), Portuguese uses construir sobre or, more idiomatically, partir de / se basear em. And note the false expectation around the participle: the adjective "well-built" is bem construído (with the accent), and "under construction" is the fixed phrase em construção (the noun), not a verb form.

Common Mistakes

Key Takeaways

• Present tense: eu construo, but você/ele constrói and vocês/eles constroem — the u shifts to a stressed ó/ói.
• constroem has NO accent under AO90; constrói keeps its acute accent because it is an oxytone ending in a diphthong.
• Accent the stressed i in hiatus: construí, construíste, construímos, construíram, construía(s), construído, construísse, construíres.
• Do not accent: construo, construiu, construindo, construirei, construir, and the subjunctive construa/construam.
• The same ói shift appears in destruir and reconstruir, but the -buir verbs (contribuir, distribuir) keep a plain i.