A sentence adverb is a type of adverb that modifies the entire sentence instead of just a single word. It is usually placed at the beginning of a sentence to indicate the speaker's attitude or opinion towards the statement that follows. Some synonyms for sentence adverb include discourse marker, adverbial connector, transitional adverb, and conjunctive adverb. Discourse markers are words or phrases that help organize speech or writing, while adverbial connectors connect two parts of a sentence. Transitional adverbs also connect ideas or clauses within a sentence, while conjunctive adverbs join two independent clauses. Regardless of their name, all these synonyms perform the same function, helping to create a cohesive and clear message in writing or speech.