onto
to place or position upon:
He put his glasses onto the table.; to be aware of:
I’m onto your wily ways.Not to be confused with:on to – go forward:
moved on to the next phase Abused, Confused, & Misused Words by Mary Embree Copyright © 2007, 2013 by Mary Embree
on·to
(ŏn′to͞o′, -tə, ôn′-)prep.1. On top of; to a position on; upon: The dog jumped onto the chair.
2. Informal Fully aware of; informed about: The police are onto the robbers' plans.
adj. Mathematics Of, relating to, or being a function such that every element of the codomain is the value that corresponds to an element in the domain.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.
onto
(ˈɒntʊ; unstressed ˈɒntə) or on to
prep1. 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.
3. into contact with: get onto the factory.
Usage: 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
Collins English Dictionary – Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014
on•to
(ˈɒn tu, ˈɔn-; unstressed ˈɒn tə, ˈɔn-)
prep. 1. to a place or position on; upon; on.
2. Informal. aware of the true nature, motive, or meaning of: I'm onto your tricks.
adj. 3. Math. pertaining to a function or map from one set to another set, the range of which is the entire second set.
[1575–85]
onto-
a combining form meaning “being”: ontogeny.
[< New Latin < Greek]
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.
onto
You usually use the preposition onto to say where someone or something falls or is put.
He fell down onto the floor.
Place the bread onto a large piece of clean white cloth.
After many verbs you can use either onto or on with the same meaning.
I fell with a crash onto the road.
He fell on the floor with a thud.
She poured some shampoo onto my hair.
Carlo poured ketchup on the beans.
However, after verbs meaning climb or lift you should use onto, rather than 'on'.
She climbed up onto his knee.
The little boy was helped onto the piano stool.
If you hold onto something, you put your hand round it or against it in order to avoid falling. After verbs meaning hold, you use onto as a preposition and on as an adverb.
She had to hold onto the edge of the table.
I couldn't put up my umbrella and hold on at the same time.
We were both hanging onto the side of the boat.
He had to hang on to avoid being washed overboard.
Onto is sometimes written as two words on to.
She sank on to a chair.
Collins COBUILD English Usage © HarperCollins Publishers 1992, 2004, 2011, 2012