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This is how the vocabulary exercises work:
Each chapter has a series of practice matching exercises, in which you have to match Greek words to English equivalents, either by dragging and dropping them, or by choosing from a drop-down list. Each chapter introduces and practices the vocabulary from that chapter of the textbook, and then reviews vocabulary from previous chapters, so that as you go through the materials, you'll see the same words coming up repeatedly. Some of the exercises use "random selection" of items, so that each time you load the exercise you'll see a different set of words from a larger set, in a different order.