<p><strong>Preposition</strong></p><ul><li>to a place or position on; upon; on: to get onto a horse.</li><li>Informal: in or into a state of awareness about: I'm onto your scheme.</li></ul><p><strong>Adjective</strong></p><ul><li>Also.</li><li>Mathematics: pertaining to a function or map from one set to another set, the range of which is the entire second set.</li></ul>