Clarification on the 'rope/line' US Navy issue.
In my experience, 'rope' was specifically used to denote wire-strand cables, and 'line', 'halyard' and the rest were used to denote anything with either natural or synthetic fiber strands.
I rather like GUEST Gareth's point on the mnemonics. Still doesn't explain one of my favorite distance problems... one 'sea song' that refers to someone taking twenty YEARS to figure out how to cross from Dublin to Devon. That's what - 100 miles? If that much? One would think that the sailor in question had other reasons than stated in the song for not going home...