

Разрежь этот лист бумаги поперёк.
Cut this sheet of paper crosswise.
Положи линейку поперёк, а не вдоль.
Put the ruler crosswise, not lengthwise.
Почему ты нарисовал полоски поперёк?
Why did you draw the stripes crosswise?
"поперёк" is in the lesson "Geometric figures" (Level 45), along with 11 other useful words. LinDuo has 180 topic lessons like this one, 2,380 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.