When I revise vocabulary with very young students, I often use basic arithmetic operations (such as adding, subtracting, multiplying, and dividing numbers). I pre-teach words like: plus, minus, times and divided by. I put 6 flashcards on the board and I number them 1-6. Then I ask, e.g. "What is 2 + 2?". My students calculate it quietly and instead of saying the right number they have to tell me what is in the picture. So their answer is "crayons" not "4".