Merriam-Webster's Collegiate® Dictionary, 11th Edition
SUDDEN
I. adjective see: sub-
Date: 14th century
1. happening or coming unexpectedly , changing angle or character all at once , marked by or manifesting abruptness or haste , made or brought about in a short time ; prompt , see: precipitate suddenly adverb suddenness noun
II. noun
Date: 1558
an unexpected occurrence ; emergency