The process whose specific outcome is the progression of the trochlear nerve over time, from its formation to the mature structure. The trochlear nerve is a motor nerve and is the only cranial nerve to exit the brain dorsally. The trochlear nerve innervates the superior oblique muscle. [ GOC:jid GOC:dph http://openisbn.com/search.php?q=0838580343&isbn=1/ GOC:cls GOC:dgh http://purl.obolibrary.org/obo/go/references/0000021 ]