Saber vs. poder for ability in Spanish (A2)

what is it?

Spanish has two verbs where English uses a single word: Saber + infinitive expresses a learned skill — something you know how to do because you have practised or studied it. Poder + infinitive expresses circumstantial possibility, physical capacity, or permission — whether conditions allow something to happen on a given occasion. Because English "can" covers both meanings, the Spanish verb must be chosen by meaning, not by translation.

when to use it

Use saber + infinitive for a skill acquired through learning or practice — swimming, playing an instrument, driving, speaking a language. The ability is general and permanent: it does not depend on today's circumstances.
Use poder + infinitive when external conditions, physical state, or permission determine whether an action is possible on a specific occasion. The pool may be closed, you may be tired, or you may need someone's authorisation.
Use poder + infinitive to ask for or grant permission (¿Puedo entrar?). Saber is never used for permission.
A quick test: if you can substitute "know how to" in English, use saber. If you can substitute "be able to" or "be allowed to" on this occasion, use poder.

formation

Both verbs are followed directly by an infinitive — no preposition, no que. The structure is: conjugated verb + infinitive.

Saber — present tense (irregular first-person singular only):

pronoun	form	meaning
yo	sé	I know how to
tú	sabes	you know how to
él / ella / usted	sabe	he / she / you know(s) how to
nosotros / nosotras	sabemos	we know how to
vosotros / vosotras	sabéis	you (pl.) know how to
ellos / ellas / ustedes	saben	they / you (pl.) know how to

Poder — present tense (stem-changing o → ue, except nosotros / vosotros):

pronoun	form	meaning
yo	puedo	I can / am able to
tú	puedes	you can / are able to
él / ella / usted	puede	he / she / you can
nosotros / nosotras	podemos	we can / are able to
vosotros / vosotras	podéis	you (pl.) can
ellos / ellas / ustedes	pueden	they / you (pl.) can

Neither verb takes a preposition before the infinitive. Say sé nadar and puedo nadar, never *sé a nadar or *puedo a nadar.

examples in context

Sé nadar, pero hoy no puedo porque la piscina está cerrada.

I can swim, but today I can't because the pool is closed.

Sé nadar = learned skill (permanent); no puedo = blocked by circumstances today.

¿Sabes tocar la guitarra?

Do you know how to play the guitar?

Asking about a learned skill — saber is the only correct choice here.

¿Puedo abrir la ventana?

Can I open the window?

Requesting permission — poder is required; saber would make no sense here.

Ella sabe hablar francés, pero hoy no puede hablar mucho porque está cansada.

She knows how to speak French, but today she can't speak much because she is tired.

Sabe hablar = acquired skill; no puede hablar = physical state prevents it on this occasion.

common pitfalls

Using poder for a learned skill. Saying *puedo tocar el piano when you mean general ability implies only that conditions happen to allow it right now, not that you have the skill. Use sé tocar el piano to state that you know how to play.
Using saber for a one-off possibility or invitation. *¿Sabes venir mañana? sounds like you are asking whether someone has learned the skill of coming tomorrow, which is nonsensical. The correct form is ¿Puedes venir mañana? — asking whether circumstances allow it.
Adding a preposition or que after saber. Forms like *sé a nadar or *sé que nadar are ungrammatical. Saber (and poder) connect directly to the infinitive: sé nadar. No linking word is needed or permitted.