onto
prep.prep. to a position on top of something. You use this when something moves from one place to another surface.
prep. to a position on or in contact with the surface of something. Indicates movement or direction toward a surface, rather than just a static location.
The cat jumped onto the table.
The workers loaded the heavy boxes onto the truck before the rain started.
The sunlight spilled onto the polished floor, highlighting the dust motes dancing in the air of the quiet library.
From on + to, after into. Compare Saterland Frisian antou (“up to”).
Used with verbs of motion to indicate the destination surface; often written as two words ('on to') in British English when 'on' is part of a phrasal verb.
The book is onto the deskThe book is on the deskOnto implies movement toward a surface; use 'on' for a static position.