

世界で一番高い山はどこですか。
いつか世界を旅行したいです。
この料理は世界中で人気があります。
"せかい(世界)" is in the lesson "Geography" (Level 22), along with 9 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.