upon /əˈpɔn/ prep.在…上面 (与on同义，on更通俗，口语化；upon显得文气。):He sat upon the grass. 他坐在草地上。A lot of extra work fell down upon my shoulders.大量的额外工作落到我肩上。once upon a time 从前 (用于故事开头)：Once upon a time there lived a king. 从前有个国王。