as an adverb (with a verb): I immediately recognized his voice. (followed by a preposition or another adverb): ♦ She’s the woman who was standing immediately next to me. ♦ Our team scored another goal almost immediately afterwards. (followed by an adjective): ♦ It was immediately obvious that there was some kind of problem.
as a conjunction (connecting two clauses) in British English: I’ll phone you immediately I hear any news.