Alerter is a noun that refers to someone or something that warns, informs, or notifies others of a specific event or situation. Other words that can be used to convey a similar meaning include notifier, announcer, messenger, herald, and harbinger. Notifier emphasizes the act of informing, while announcer is associated with broadcasting and public announcements. Messenger and herald often imply urgency and importance. Harbinger, on the other hand, conveys a sense of ominous or prophetic warning. So, depending on the context in which the word is used, there are several synonyms for alerter that can add nuance and clarity to the intended meaning of the sentence.