

箱の側面に名前を書いてください。
円柱の側面の面積を計算してみましょう。
立方体の側面は全部正方形ですか。
"そくめん(側面)" 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.