The bull, which is in the pasture , belongs to Joe. A pronoun must always refer specifically to one noun. The word which is often used incorrectly. Adverb clauses function as adverbs in the sentence, modifying verbs, adjectives, or adverbs. They may tell how , why, when, where, etc.
Conjunctions used include although, after, if, because, while, since, whether.
When I arrived at the University , classes had already started. Stan is happy because he got a high grade on his history midterm. Although Bob is intelligent, he doesn't work very hard. It usually lacks either a subject or a verb, or both. For example, three dogs and a goat.