突然

1. Origins, structure, and basic meaning

• Structure: 突然 (とつぜん) is a noun and adverbial expression meaning suddenly or without warning.
• Basic usage: It emphasizes the unexpected onset of weather or an abrupt action by a person.
  • 歩いていると、突然雨が降り始めました。 — It suddenly began to rain while I was walking.
  • 彼が突然立ち上がったので、皆が驚きました。 — Everyone was surprised when he abruptly stood up.

2. Common pitfalls and similar expressions

• Unexpected occurrence
  • 急に also means suddenly, while 突然 can place stronger emphasis on an event occurring without warning.