s]
noun, verb, -posed, -pos⋅ing.| 1. | the reason for which something exists or is done, made, used, etc. |
| 2. | an intended or desired result; end; aim; goal. |
| 3. | determination; resoluteness. |
| 4. | the subject in hand; the point at issue. |
| 5. | practical result, effect, or advantage: to act to good purpose. |
| 6. | to set as an aim, intention, or goal for oneself. |
| 7. | to intend; design. |
| 8. | to resolve (to do something): He purposed to change his way of life radically. |
| 9. | to have a purpose. |
| 10. | on purpose, by design; intentionally: How could you do such a thing on purpose? |
| 11. | to the purpose, relevant; to the point: Her objections were not to the purpose. |

pur·pose (pûr'pəs) n.
To intend or resolve to perform or accomplish. [Middle English purpos, from Anglo-Norman, from purposer, to intend : pur-, forth (from Latin prō-; see pro-1) + poser, to put; see pose1.] |
on purpose
Deliberately, intentionally, as in He left the photo out of the story on purpose. Shakespeare's use of this idiom was among the earliest; it appears in The Comedy of Errors (4:3): "On purpose shut the doors against his way."
accidentally on purpose. Seemingly accidentally but actually deliberately, as in She stepped on his foot accidentally on purpose. This generally jocular phrase was first recorded in 1862.