journal. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000. diary. The American HeritageŽ Dictionary of the English Language: Fourth Edition. 2000.
There's a fair amount of overlap; you'll see that one of the meanings given for
diary is
journal. In most cases, though, it's a question of substance - a 'journal' (in contexts that overlap with
diary, that is, excluding usages like
Wall Street Journal) is usually more substantial than a diary; in fact, one sort of diary is called a 'page-a-day diary', and a journal is normally more than that.
b