How is Alert used a sentence as noun and verb?

The noun 'alert' can function as the subject of a sentence or a clause, and as the object of a verb or a preposition. Example sentences:

• An alert will be given when the limo arrives. (subject of the sentence)
• We heard the alert that the limo had arrived. (direct object of the verb 'heard')

The verb 'alert' can function as a main verb or an auxiliary verb. Example sentences:

• Please alert the chef that we have an extra guest. (main verb)
• The chef will alert us when to seat the guests. (auxiliary verb)