

子供は何人いますか。
子供の時、よく川で泳ぎました。
この映画は子供も見られます。
"こども(子供)" is in the lesson "Family 2" (Level 24), along with 13 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.