[ on-too, awn-; unstressed on-tuh, awn- ]
See synonyms for onto on Thesaurus.com
  1. to a place or position on; upon; on: to get onto a horse.

  2. Informal. in or into a state of awareness about: I'm onto your scheme.

  1. Also surjective .Mathematics. pertaining to a function or map from one set to another set, the range of which is the entire second set.

Origin of onto

First recorded in 1575–85; on + to

Words that may be confused with onto

Other definitions for onto- (2 of 2)


  1. a combining form meaning “being,” used in the formation of compound words: ontogeny.

Origin of onto-

<New Latin <Greek ont- (stem of ón, neuter present participle of eînai to be) + -o--o-
  • Also especially before a vowel, ont-.

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2024

How to use onto in a sentence

  • Mr. Hartley smiles to himself as he disappears in the wings; he is "on-to" the little tricks of stars and leading ladies.

    My Actor-Husband | Anonymous

British Dictionary definitions for onto (1 of 2)


on to

/ (ˈɒntʊ, unstressed ˈɒntə) /

  1. to a position that is on: step onto the train as it passes

  2. having become aware of (something illicit or secret): the police are onto us

  1. into contact with: get onto the factory

usage For onto

Onto is now generally accepted as a word in its own right. On to is still used, however, where on is considered to be part of the verb: he moved on to a different town as contrasted with he jumped onto the stage

British Dictionary definitions for onto- (2 of 2)


combining form
  1. existence or being: ontogeny; ontology

Origin of onto-

from Late Greek, from ōn (stem ont-) being, present participle of einai to be

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Other Idioms and Phrases with onto


see be on to.

The American Heritage® Idioms Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.