In short

The verbs you reach for most often - ser, estar, ter, ir, vir, fazer, poder - break the neat patterns of Lesson 6, so they have to be learned as whole forms rather than built from a stem. Between the fully regular verbs and these outright irregulars sits a large, well-behaved middle group: -ir verbs that are regular everywhere except the eu form, where the stem vowel shifts (prefiro, visto, durmo). Master the eu forms and you have tamed most of the difficulty, because that is exactly where Portuguese irregularity hides.

The rule

Vowel-alternation verbs: only the eu form changes

A big family of -ir verbs whose stem vowel is e or o raise that vowel in the eu form only: e -> i and o -> u. Every other person keeps the original vowel and the regular -ir endings from Lesson 6.

• preferir (to prefer): prefiro, but preferes, prefere, preferimos, preferem.
• vestir (to dress): visto, but vestes, veste…
• sentir (to feel): sinto, but sentes, sente…
• servir (to serve): sirvo, but serves, serve…
• dormir (to sleep): durmo, but dormes, dorme…

So the trap is narrow: say prefiro and durmo for “I”, but never carry the shifted vowel into the other persons (preferes, not prefires; dormes, not durmes).

The high-frequency irregulars

A handful of extremely common verbs have present forms you simply memorise. Their eu forms are the least guessable of all, so drill those first:

• ser “to be” (identity): sou, és, é, somos, são.
• estar “to be” (state, location): estou, estás, está, estamos, estão.
• ter “to have”: tenho, tens, tem, temos, têm.
• ir “to go”: vou, vais, vai, vamos, vão.
• vir “to come”: venho, vens, vem, vimos, vêm.
• fazer “to do / make”: faço, fazes, faz, fazemos, fazem.
• poder “can, to be able”: posso, podes, pode, podemos, podem.

Ser and estar both translate English “to be”; which one to use, and how ter and haver divide up “to have” and “there is”, is the whole of Lesson 8 - here just fix their forms in memory.

Watch the accented third persons

Two of these verbs mark the third-person plural with a circumflex to keep it apart from the singular, which is otherwise spelled the same:

• ter: ele tem (singular) vs eles têm (plural).
• vir: ela vem (singular) vs elas vêm (plural).

In speech the plural is a touch longer; in writing the accent is obligatory - dropping it changes the meaning from “they” to “he/she”.

saber vs conhecer: two ways to “know”

English “know” splits into two Portuguese verbs, and choosing the wrong one is a giveaway:

• saber = to know a fact, or to know how to do something (saber + infinitive). Its eu form is irregular: sei, sabes, sabe, sabemos, sabem. So Sei a resposta (“I know the answer”), Sabes nadar? (“Can you / do you know how to swim?”), Não sei (“I don’t know”).
• conhecer = to be acquainted with a person, a place, or a thing. It is regular apart from the spelling of the eu form, which takes ç to keep its soft sound: conheço, conheces, conhece, conhecemos, conhecem. So Conheço a Maria, Conheces Lisboa?

Rule of thumb: if you could rephrase it as “I know that…” or “I know how to…”, use saber; if it is “I know this person / place”, use conhecer.

Giving an opinion, revisited

With saber and achar (Lesson 6) you can already qualify what you say: Acho que sim, mas não sei ao certo (“I think so, but I’m not sure”).

Forms & patterns

Vowel-alternation -ir verbs - note that only the eu column shifts:

The principal irregular verbs:

Choosing between the two “know” verbs:

Examples

Common mistakes

• eu prefero, eu dormo -> prefiro, durmo - the eu form of these -ir verbs raises the vowel (e -> i, o -> u); do not spread it to the other persons (preferes, dormes).
• conheço que fica longe -> sei que fica longe - facts take saber, never conhecer. Use conhecer only for people, places and things.
• sei a tua irmã -> conheço a tua irmã - people are known with conhecer, not saber.
• conheço nadar -> sei nadar - “to know how to” is saber + infinitive.
• eu fazo, eu sabo, eu podo -> faço, sei, posso - these eu forms are memorised irregulars, not built from the stem.
• eles tem, elas vem -> eles têm, elas vêm - the third-person plural of ter and vir needs the circumflex; without it the word reads as “he/she”.
• tu és used for polite address, e.g. o senhor és -> o senhor é - você and o senhor / a senhora take the third-person form (é, tem, vem), like ele / ela.

Tips

• Attack the eu forms first - sou, estou, tenho, vou, venho, faço, posso, sei - since they are the most irregular part of each verb and the ones you say constantly.
• For the vowel-alternation group, learn the pair “eu-form vs the-rest” (prefiro / preferes, durmo / dormes); everything after the eu form is regular.
• Sort your “knows”: saber pairs with a fact or an infinitive, conhecer pairs with a name or a place. Test yourself by trying “I know that…” (saber) versus “I know this person” (conhecer).
• Hear tem vs têm and vem vs vêm as singular vs plural; in writing, never leave off the plural circumflex.
• These verbs carry most of your everyday speech, so the time you spend memorising them pays back faster than any regular verb would.
• In Brazil: the forms above are the same, but speakers use você with the third-person endings far more than tu, so you will hear você tem, você vem, você sabe where Portugal often says tens, vens, sabes.