sé

In a sentence

• Sé que arribaràs tard perquè plou.

  I know you will arrive late because it's raining.

  In this sentence, 'sé' translates to 'I know' in English and is the first person singular present indicative form of the verb 'saber', meaning 'to know'.

• No sé com funciona aquest aparell.

  I don't know how this device works.

  Here, 'sé' is used in a negative form 'no sé', which means 'I don't know', again indicating the speaker's lack of knowledge in the present tense.

• Sé tocar la guitarra bastant bé.

  I know how to play the guitar quite well.

  In this example, 'sé' indicates the speaker's ability or skill, as a part of the more general meaning of 'saber' which encompasses 'to know how (to do something)'.