

紙に丸い穴を開けました。
この板の穴は四角ですか。
靴下に穴があります。
"あな(穴)" is in the lesson "Geometric figures" (Level 45), 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.