What is the difference between "rate" and "grade"?

What is the difference between "rate" and "grade"?

When I am awarding points 0-20 for a homework assignment, do I rate the homework or do I grade it? Or perhaps both are appropriate?

In the US, in the field of eduction, the more traditional term for evaluating a student's performance on a test, or in a course, is grade, although more recently, perhaps because of the onset of standardized testing, the word score has gained wider usage, although that word is used mostly for single events, so that one would give (or receive) a score on a test, but a grade for the class. The words rate and score also usually suggest that there is an objective standard, with right and wrong answers, or is the result of the calculation by which the set of grades earned in tests, and other items evaluated yield a final result.

On the other hand, rate implies a more subjective evaluation, perhaps one which does not have right or wrong answers. So an instructor might be said to rate a student's performance in the course in a category of "classroom participation", which may not lend itself well to an objective standard.

Outside of education, again in the US, "grade" is frequently used to describe measures of quality. So that in the case of lumber a knowledgeable buyer knows from the grade that a particular piece of lumber will have certain characteristics that fall within a certain range of values. Similarly, in agriculture, "grades" are defined for most types of agricultural products. Most milk sold in the US, for example, has characteristics that qualify it for "USDA Grade A" status, as do many of the eggs, butter, grain, meat, and other products. In all o these cases, as well as many others, the grade assigned to a particular item is an evaluation of how a particular item compares with certain characteristics deemed important.

Rate, is commonly used when there is a numerical ratio involved, so one speaks of a "rate of interest" on a savings account, or on a loan. The cost of certain types of commodities, such as water, electricity, fuel, and other items priced on a per unit basis is usually called a rate.

When used specifically for awarding points/marks on an assignment, I would recommend using grade.

If you use rate, it'll be more like if someone asked you to rate the quality of the assignment, say Rate this assignment on a scale of 1 to 10.

Using grade, therefore, doesn't leave any room for ambiguity.