Word Check: In spite of vs. Despite

Students today asked if there is a difference in meaning between the two.

After much debate, I said there is none. The thing is to remember to insert that sneaky and oft-neglected preposition, "of".

What exactly do in spite of and despite mean?

It's used to express contrast between two clauses. For instance:

Despite the rains, people still lined up to pay their last respects to the late President.
In spite of the rains, people still lined up to pay their last respects to the late President.

Note that a comma is necessary to mark the end of the clause with the adverb (adverb clause) if it is positioned before the main clause.

1st: Despite the rains ( , ) = adverb clause
2nd: people still lined up to pay their last respects to the late President. = main clause

If the adverb clause comes after the main clause, then a comma is no longer needed. For instance:

People still lined up to pay their last respects to the President despite the rains.
People still lined up to pay their last respects to the President in spite of the rains.

1st: People still lined up to pay their last respects to the late President = main clause
2nd: in spite of the rains. = adverb clause

I've been using the word "clause" a lot in this entry. To clarify, a clause technically is different from a phrase in the way that is has both a subject and a predicate. Note that the main clause can have meaning and stand alone even without the adverb clause. The adverb clause, however, is considered correct and makes sense only if it is used with the main clause.