what is the difference between a noun clause in apposition and an adjective clause?
Answers
My dream, that I might return once more to Africa, came true with last year’s visit.
The clause that I might return once more to Africa functions as an appositive, to explain further the meaning of my dream. It is not a defining relative (=adjective) clause, because dream is already defined by the possessive adjective my, which is a determiner, i.e. which defines. Listen to the way the sentence is spoken. Sense the pause introduced by the commas. The pronoun that introduces the clause, but it does not substitute for a noun in the main clause.
A relative clause (an adjective clause) beginning with that is necessarily a defining clause, and it is not set off by commas.
The dream that I might some day return to Africa came true with last year’s visit.
The clause answers the question Which dream?
P.S. The opposite of a defining clause is a non-defining clause. It provides “extra” information and it is set off by commas. For things or ideas it begins most often with which rather than that.
My dream, which involved returning to Africa, came true last year. Which means the same as my dream in the main clause. The clause provides extra, non-defining information about the subject my dream.