I.on [美 ɑn, ɔn, 英 ɒn]介词on often appears as the second element of certain verb structures in English (count on, lay on, sign on, etc). For translations, see the relevant verb entry (count, lay, sign, etc).
He was gaunt, unshaven, greasy-skinned, a stark sleepless half-crazy look on his slightly potato-like facehad come down after a night's work for a cup of coffee.