

突然雨が降り出しました。
会議中に突然電気が消えてしまいました。
彼は突然会社を辞めたんですか。
"とつぜん(突然)" is in the lesson "When" (Level 42), along with 11 other useful words. LinDuo has 180 topic lessons like this one, 2,379 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.