Advice and ability: dever and saber

dever: Softer Than ter de

Ter de says you HAVE to; dever says you SHOULD. It conjugates like any regular -er verb — devo, deves, deve, devemos, devem — and connects directly to an infinitive, no preposition:

You should eat breakfast.
Deves comer o pequeno-almoço.
He should sleep: he is tired.
Ele deve dormir: está cansado.
I should study today.
Devo estudar hoje.

Negated, it is advice against: We should not drink coffee at night.

Não devemos beber café à noite.

saber + Infinitive: Learned Ability

Poder is can in the sense of permission or possibility. For a SKILL — something you learned — Portuguese uses saber (to know) + infinitive: to know how to.

Its present is regular except the eu-form sei: sei, sabes, sabe, sabemos, sabem.

I can speak Portuguese and English.
Sei falar português e inglês.
Do you know how to make dinner? — I do.
Sabes fazer o jantar? — Sei.
She can read Portuguese.
Ela sabe ler português.

Compare: Ela pode ler — she may / is able to right now; Ela sabe ler — she has learned to. English says can for both; Portuguese never confuses them.

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