

夏休みのあいだ、国に帰ります。
留守のあいだ、猫をお願いします。
会議のあいだは、電話に出られません。
"のあいだ" is in the lesson "Time 2" (Level 35), 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.