

コンビニのコーヒーは安くて便利です。
この水筒は便利ですか。
ペットボトルのお茶は便利だね。
"べんり(便利)" is in the lesson "Drinks" (Level 40), 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.