How to use いきなり, 急に and 突然 the Right Way
I’d say some people don’t get a nuance of these words, いきなり, 急に and 突然 because all can be translated to “Suddenly”. And I’d say you would quite often hear these words from natives using it, so let’s figure them out the way to use in this time.
Suddenly / Abruptly (process, no preparation, reckless and from the beginning)
いきなり can be used as events that you didn’t expect and it went through an appropriate “process” and has the meaning of “suddenly”. You could use いきなり such as below, however, 急に and 突然 basically don’t have the meaning of “the process”. So using 急に and 突然 are not correct in this case.
Suddenly / Abruptly / Unexpectedly
急に is used that something events unexpectedly happened for you. And also いきなり is adjective so it explains about nouns, however, 急に is the adverb, so this would explain verbs and adjective.
Suddenly / All of a sudden / Unexpectedly (formal/happened event)
突然 means almost same as equal as 急に and more formal than 急に, so 突然 is often used as a writing or formal word. And suddenly, something momentarily happened.