Definition of: upon

(ə·pon′, ə·pôn′) prep.
1. On, in all its meanings.
2. On, in an elevated position: upon the throne.
3. On, by motion upward: to get upon a roof.
—adverb On: completing a verbal idea: The paper has been written upon. Also Scot. up·o′. See synonyms under ABOVE. [ME]♦ Upon now differs little in use from on, the former being sometimes used for reasons of euphony and also preferably when motion into position is involved, the latter when merely rest or support is to be indicated. When upon has its original meaning of up and on, it is written as two words, up having its adverbial force: Let us go up on the roof.