sorting, grading, and classifying
These are one of those cases when the context may matter a lot.
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In general
grading, Attributing a catgeory, possibly numeric. Grade these apples into the 4 size categories that we sell.
Grade a test = attribute a mark/score to it, or every paper.
Make the grade = get a high enough score for something.
classifying - assign one of multiple categories, that is countable options. red or yellow, Bigger than a breadbox, or smaller
sorting, Can mean the same as grading, but in general means, puting in order. "Order" may mean categories. All the red ones go in this box.
But, can also mean into an order.
Arrange (sort) these into size order, ascending in size, sm,allest over there and largest here.