viajarán

In a sentence

• Ellos viajarán a España el próximo verano.

  They will travel to Spain next summer.

  Here, 'viajarán' is used in its simple future tense form to indicate an action (traveling) that will happen in the future.

• Pienso que viajarán mucho si tienen más tiempo libre.

  I think they would travel a lot if they have more free time.

  In this case, 'viajarán' implies a hypothetical future action subject to the condition of having free time, although in formal language 'viajarían' might be used for hypothesis.

• ¿Cuándo viajarán ustedes a Argentina para las vacaciones?

  When will you all travel to Argentina for the holiday?

  Here, 'viajarán' asks about the time of the planned future action of traveling, directed towards the second person plural form 'ustedes'.