Recur comes from Latin recurrere ('to run back, return'), from re- ('back, again') + currere ('to run'). The prefix supplies the first semantic turn, while the base carries the lexical core of the word. As a verb, it means "to occur again, repeatedly, or periodically", so the modern sense keeps the older action or relation visible. Relevant historical forms include Latin re-, Latin recurrere, and Latin currere. Derivative forms include recurrence, recurrent, recurring, recurred; related words include recursive, occur, current, concur.