Caber

Caber means to fit — to have enough room. It is an irregular -er verb, and its irregularities cluster in exactly the places you would expect for a verb of its family: a quirky 1st-person singular present (caibo), and an entire branch of forms built on a "strong" preterite stem (coub-). Because caber expresses a physical or abstract notion of having space for something, it behaves a little unusually in syntax too: the thing that fits is usually the subject, and the place is introduced by em.

Core meaning: to fit / to have room

The most common use: something fits (or doesn't) somewhere.

Notice the structure: the thing that fits (nada, esse sofá) is the subject, and the place is a prepositional phrase with em (na mala, na sala). English often says "fit X into Y" with a person as subject ("I can't fit anything into the suitcase"), but Portuguese makes the object the subject: nada cabe na mala.

The idiom: caber a alguém

A very common figurative use is caber a alguém = to be someone's responsibility / role / turn; "to fall to someone (to do something)."

This caber a is parallel to English "it falls to me / it's up to you." It is slightly formal but extremely common in writing, news, and thoughtful speech.

The irregularities — read carefully

There are two irregular zones. Everything else is regular -er.

Zone 1 — the present-tense 1sg "caibo." The eu form is caibo (an inserted i), but the rest of the present is regular: cabe, cabemos, cabem. This same caib- stem then drives the entire present subjunctive (caiba, caibamos, caibam) and the você/vocês imperative.

Zone 2 — the strong preterite stem "coub-." Like poder→pude, saber→soube, and haver→houve, caber has a "strong" (rhizotonic) preterite: coube. From this coub- stem come three whole tenses: the pretérito perfeito (coube, coubemos, couberam), the imperfeito do subjuntivo (coubesse), and the futuro do subjuntivo (couber).

Conjugation

Presente do indicativo

Pretérito perfeito

Note that eu and ele/ela are both coube — they are spelled and pronounced identically (unlike poder, where 1sg pude differs from 3sg pôde). With caber, only the subject pronoun and context distinguish "I fit" from "he fit."

Pretérito imperfeito

The imperfect is regular (built on the cab- stem): cabia, cabíamos, cabiam.

Futuro do presente

Futuro do pretérito (conditional)

The future and conditional are regular (built on the full infinitive caber-).

Presente do subjuntivo

Imperfeito do subjuntivo

Futuro do subjuntivo

Imperativo

The imperative of caber is rare in practice (you seldom command something to fit), but the standard forms come from the subjunctive: caiba, caibam.

Formas nominais (non-finite)

Usage in context

False-friend / confusion notes

Caber has no English false friend, but two confusions are worth flagging:

• Do not confuse caber (to fit) with cair (to fall) — they look similar but are unrelated verbs with very different conjugations (cair → caio, caí, caísse).
• The "to be up to someone" idiom uses caber a, not caber para or caber em. The preposition a is fixed here.

Spanish speakers should note that Portuguese caber and Spanish caber are cousins, but the strong preterite differs in spelling: Spanish cupe/cupo, Portuguese coube. Don't import the Spanish cup- stem.

PT-PT contrast

Caber conjugates identically in European and Brazilian Portuguese — the irregular forms (caibo, coube, caiba, couber) are shared. The idiom caber a alguém is equally current in both. As always, the progressive differs: não está a caber (PT) vs. não está cabendo (BR), though with caber the simple present (não cabe) is far more usual than any progressive.

Common Mistakes

The single biggest error is regularizing the irregular stems — saying cabo (should be caibo) or caberam (should be couberam). There is no logical shortcut: caber is irregular because it inherited a Latin strong perfect, and you simply must lock in the four anchors — caibo, coube, caiba, couber.