Ports and marine works

Twenty-fourth in the list is a deriva litoral, and the first noun has a river inside it that English cannot see, because for this one job it reaches into the other family. A deriva goes back to Latin derivare, which was not an abstract verb at all: de plus rivus, the stream, it meant to lead water away out of a watercourse, to take it off its channel. Everything the word does now, in either language, is that picture generalised. A ship à deriva has been taken off its own channel by something stronger than itself; a mathematician taking a derivative and a scholar deriving one form from an older one are leading the same water away from the same stream. English kept the abstract branch, calls it « to derive », and it sounds like a seminar. For the thing this list names it takes a Germanic word instead, « drift », the noun that belongs to « drive »: what has been driven. So « longshore drift » says who pushed the sand along, and a deriva litoral says which channel it left.