"Todd left camp before I had a chance to say goodbye".
"Hilda always eats five eggs with toast before she leaves for school".
Traditional grammar calls the underlined expressions "Adverb clauses".
But modern grammar does not use the terms "adverb clause" / "adjective clause" / "noun clause".
Instead, the word "before" is treated as a preposition and the rest of the expression is simply called a "subordinate clause". The whole preposition phrase is then said to be functioning as a "temporal adjunct".