Each word has a number of slightly different meanings. I am going to explain the difference between one meaning for "grade" and one for "rank." A grade is a measurement on some scale. Because it is a measurement, they could fall anywhere. For example, on the first exam Alex gets a grade of 90, Blake a grade of 89, Casey a grade of 60. On the second, Alex gets 89, Blake gets 63, Alex gets 59. To get the "rank," numbers are ranged in order and then assigned successive ranks. On the first exam, Alex ranks #1, Blake ranks #2, Casey ranks #3. On the second exam, despite getting different grades, Alex still ranks #1, Blake still ranks #2, and Casey still ranks #3.

They are very similar but grading is for certain things such as school grades, but ranking is for example for the military general captain, eggs also have grades. So I think when you can give “a number”, such as 50 or A, B, C” it’s a grade but if it’s a word such as lieutenant it’s a rank because it’s a position

I'll compare the verbs, not the nouns. "To rank" things means to place them in some sort of order, e.g. best to worst, smallest to largest, cheapest to most expensive, and so forth. "To grade" things means to assign each one some sort of value, e.g. a score on a test, a monetary value, a size in meters, and so forth. If you have graded things, that gives you values that you can use to place those things in order (rank them) if you want. You can use one (grade) in order to do the other (rank) so the ideas are related, but they are not the same. They are not synonyms.

As Bethy said the context is important, but also "grade" is often used to say someone or something has reached a particular level, whereas "rank" is often used in comparison to another similar thing. Imagine an exam where people can score between 0 and 100. We could assign grades to certain scores. For example: 0-25 = No grade 26-50= grade C 51=75= grade B 76-100 = grade A Then imagine that all the students scored between 51-75. We could say that they all achieved grade B. But then we might want to know which students performed best. We could then rank them in order. For example: Sarah - 73 Mohammed - 70 Arthur - 67 etc We could then say that Sarah ranked above everyone, whilst Mohammed ranked above Arthur, etc.

не з того боку підхід до ситуації -- майже однакові за значенням вони просто вживаються з різними словами тож в залежності від того яке наступне слово вибір впаде на grade або rank