let

In a sentence

• Už je to deset let, co jsme se neviděli.

  It has been ten years since we last saw each other.

  In this sentence, 'let' is used as a noun to mean 'years', which is the plural of 'rok' (year). It denotes a period of time.

• Let ptáků vypadá elegantně na obloze.

  The flight of birds looks elegant in the sky.

  Here, 'let' functions as a noun meaning 'flight', describing the act or process of flying.

• Letím do Paříže zítra ráno.

  I am flying to Paris tomorrow morning.

  In this instance, 'letím' is a conjugated verb form meaning 'I am flying'. It comes from the verb 'letět' which means 'to fly'.