# onto

/ˈɑntu/ (US) · /ˈɒntʊ/ (UK)

Source: https://englishreference.com/word/onto
Updated: 2026-08-08

## Senses

### 1. movement to a surface

preposition · CEFR A2

to a position on the surface of something.

For teachers: indicating movement toward a position on or atop a surface.

- The cat jumped onto the kitchen table to reach the food.
- The hikers climbed onto the rocky ledge to get a better view of the valley below as the fog began to clear.

### 2. aware of a secret

preposition · CEFR B2 · Informal

knowing about someone's secret or bad behavior.

For teachers: indicating awareness of someone's true intentions or illicit activities.

- The police are onto his plan, so he will probably be caught soon.
- The manager realised the staff were onto her strategy to reduce overtime, leading to a tense meeting on Monday morning.

### 3. surjective

adjective · CEFR C2 · Technical

a special type of math rule where every possible result is used.

For teachers: describing a function where every element in the codomain is the image of at least one element from the domain.

- In this math problem, we need to prove that the function is onto.
- The professor demonstrated that while the mapping was continuous, it was not onto, as several values in the target set remained unreached.

Usage: In mathematics, this is often used as a predicative adjective following the verb 'to be'.

## Examples

- 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.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.