Irregular Verb Groups

Portuguese has a reputation for irregular verbs. Learners see names like trouxe, soube, couber, farei, dir-se-ia and freeze up. The good news — the news this page is built on — is that Portuguese irregulars are not a random heap. They fall into a small number of well-defined patterns, and once you know which pattern a verb belongs to, you can predict its entire conjugation. The job of this page is to give you those patterns.

The eight groups below cover essentially every irregular verb in modern European Portuguese. Some verbs belong to more than one group (a contracted future plus a strong preterite, for example — that is fazer). A verb that fits none of these groups is either fully regular, a stem-changer covered in classes, or one of the handful of genuinely unique irregulars (ser, estar, ir, haver) that each need their own page.

The eight irregularity groups

Group 1: Radical change o → u

A small family of -ir verbs with stem vowel o raises that vowel to u in two places: the 1sg present indicative and the entire present subjunctive. Everywhere else, the o stays. This is a purely phonological alternation inherited from Latin vowel raising before high-vowel endings.

Member verbs

Subir is the mirror image: its infinitive already has u, and the non-1sg present indicative forms lower the vowel to o (subo, sobes, sobe, subimos, sobem). The logic is the same — unstressed high vowel u stays, stressed position becomes mid-vowel o. But you have to remember which way each verb leans.

See o-to-u stem changes for the full paradigms.

Group 2: Radical change e → i

The larger sister of Group 1. -ir verbs with stem vowel e raise it to i in the 1sg present and throughout the present subjunctive.

Member verbs (most common)

Note on pedir and medir: these also trigger a spelling change — d becomes ç before the raised vowel (pedir → peço, peça), because the original Latin stem was pet- with a palatalised consonant.

See e-to-i stem changes.

Group 3: Highly irregular auxiliaries

Five verbs are so central, so frequent, and so phonologically worn-down by use that they each need their own page. Their paradigms cannot be predicted from any general rule. You learn them by rote.

Ser, estar, ter, haver, ir — present indicative at a glance

Preterites (watch out — foi is shared by ser and ir)

Yes — ser and ir have exactly the same preterite. Context disambiguates in almost every case.

Group 4: Contracted future and conditional

A very small set of verbs contract their infinitive stem before the future and conditional endings. The future endings -ei, -ás, -á, -emos, -eis, -ão and conditional endings -ia, -ias, -ia, -íamos, -íeis, -iam normally attach to the whole infinitive (falar-ei, comer-ia). But four verbs drop consonants first:

Once you have the contracted stem, attach the normal future or conditional endings and you are done. Note that pôr's future looks like regular por- + future endings (the stem just happens to be the preposition por).

Group 5: Strong preterites

A "strong preterite" is a past tense with (1) an unpredictable stem and (2) unexpected endings — specifically, unstressed 1sg -e (instead of the regular -ei or -i) and unstressed 3sg -e (instead of -ou or -eu). This is the single most distinctive feature of Portuguese irregular verbs. Once you recognise the pattern, you recognise the verb.

The twelve strong preterites

The same stems serve as the basis for the imperfect subjunctive (fizesse, dissesse, trouxesse...) and the future subjunctive (fizer, disser, trouxer...). Learn the strong preterite stem once, and you get three tenses for the price of one.

Group 6: The -uir class

-uir verbs — infinitives ending in -uir where the u is pronounced as part of the stem (not silent) — follow a small but consistent pattern:

Key points:

• 1sg ends in -uo (not -uio).
• 3sg / 2sg have a dipthong change in some members: construir takes the open ó — constrói, constróis — a written acute to mark the open vowel.
• 3pl ends in -oem or -uem depending on the verb's vowel pattern.

Member verbs: construir, incluir, excluir, possuir, destruir, diminuir, atribuir, distribuir, influir, retribuir, contribuir, substituir. See -uir class.

Group 7: The -uzir class

-uzir verbs (produzir, conduzir, traduzir...) have one specific quirk: the 3sg present indicative drops the ending vowel, ending in a bare consonant.

Notice produz, conduz, traduz without a final vowel. The same truncation occurs in the 2sg affirmative imperative (conduz com cuidado! — "drive carefully!").

Member verbs: produzir, conduzir, traduzir, reduzir, introduzir, reproduzir, deduzir, seduzir, induzir. See -uzir class.

Group 8: The -iar class (two patterns)

-iar verbs split into two unpredictable subgroups. You have to memorise which subgroup each verb belongs to:

Pattern A: the stem raises to -ei- in the stressed present forms

Member verbs (Pattern A): odiar, incendiar, mediar, remediar, ansiar, premiar. There is a short mnemonic: O-I-M-A-P — odiar, incendiar, mediar, ansiar, premiar — these five are the ones that raise.

Pattern B: the stem stays -i- throughout

Member verbs (Pattern B): variar, copiar, anunciar, pronunciar, iniciar, apreciar, enunciar, negociar, associar. This is the vastly larger group. If you do not recognise the verb as one of the small Pattern A group, default to Pattern B.

See verbs ending in -iar for the full list.

Quick reference: which group does this verb belong to?

Common mistakes

What to focus on first

If you are building up irregular verbs in order of return on investment:

1. Group 3 first — ser, estar, ter, ir, haver. Top five words in every Portuguese conversation.
2. Group 5 next — the strong preterites. They give you the past stems you need everywhere.
3. Group 4 — the contracted futures of fazer, dizer, trazer, pôr. Appears constantly in writing.
4. Groups 1 and 2 — the stem-changers. These are the trickiest to internalise but reward close attention.
5. Groups 6, 7, 8 — regular in their own pattern. Once you notice them, they are easy.

For the full paradigms of each group, follow the links embedded above, or see the complete irregular verb guide.