rely

rely — verb

1. to need someone or something in order to keep living, working, or existing — a f

1.verbintransitiveB1
Definition

to need someone or something in order to keep living, working, or existing — a factory relies on its power supply, or an older parent relies on adult children for everyday help.

Example

After the flood destroyed her apartment, Aoi relied on friends for a place to sleep.

rely on + noun + for + noun (dependency pattern)

The village clinic relies on a single generator to keep vaccines cold during power cuts.

rely on + noun + to-infinitive (organisation)

Common collocations
  • rely on somebody for something
  • rely on something for survival
  • rely on a/an [resource/system/person]
  • rely heavily on
  • rely entirely on
  • rely solely on
  • can/could rely on
Synonyms
  • depend on

    interchangeable with 'rely on' in this sense; no difference in meaning or register

  • count on

    slightly more informal; emphasises expectation rather than need

  • lean on

    more informal; often suggests emotional or personal support rather than material help

Antonyms

Grammar Patterns

rely on/upon + noun/pronoun

rely on/upon + noun/pronoun + for + noun

rely on/upon + noun/pronoun + to-infinitive

Usage Note

Always used with the preposition 'on' (or, more formally, 'upon'). The object of the preposition names the source of support. Do not write or say 'rely' without a preposition — 'I rely my brother' is incorrect.

Common Mistakes

She relies her parents for money.
She relies on her parents for money.
'Rely' must always be followed by 'on' (or 'upon') before the object.
The system relies to work properly.
The system relies on regular updates to work properly.
'Rely' cannot take a to-infinitive directly; it needs an object after 'on'.

2. to feel certain that someone will do what they have promised or that a piece of

2.verbintransitiveB1
Definition

to feel certain that someone will do what they have promised or that a piece of information is correct — for example, relying on a friend to keep a secret, or relying on a weather forecast when planning an outdoor event.

Example

Christopher relied on the train timetable, but the 7:15 service was cancelled without any notice.

rely on + information that proves wrong

Lucía relied on her best friend to keep the secret until the right moment.

rely on + person + to-infinitive (trust)

Common collocations
  • rely on somebody to do something
  • can/could rely on
  • should be able to rely on
  • always rely on
  • rely on [word/information/promise/report]
  • rely on [instinct/gut feeling]
Synonyms
  • trust

    broader meaning and does not require the preposition 'on'; 'trust someone' vs 'rely on someone'

  • count on

    more informal; interchangeable in most trust-related contexts

  • bank on

    informal; expresses strong expectation that something will happen

Antonyms
  • distrust

    strong opposite — actively doubt someone's reliability

  • doubt

    less strong than distrust; questions the truth or reliability of something

Grammar Patterns

rely on/upon + noun/pronoun + to-infinitive

rely on/upon + noun/pronoun

Usage Note

Always used with 'on' or 'upon'. This sense emphasises trust and confidence, not material need. It is often used with modal verbs such as 'can', 'could', 'should', and 'must'. The structure 'rely on + object + to-infinitive' is the most common pattern for expressing trust in a person's action.

Common Mistakes

I rely you to keep quiet.
I rely on you to keep quiet.
Same preposition rule as sense 1: 'on' must follow 'rely'.
I rely that the information is correct.
I rely on the information being correct.' or 'I trust that the information is correct.
'Rely' cannot introduce a that-clause.

Word family

Synonym discussion

Sense: verb/2

'Rely on' and 'count on' are very close in meaning and register — both suggest confident expectation that someone will act or something will happen. 'Count on' feels slightly more personal and is common in everyday speech ('You can count on me'). 'Trust' is broader: it does not require a preposition and covers emotional confidence in a person's character, not just their specific actions. 'Bank on' is informal and emphatic, used when the speaker has a strong stake in the outcome ('I wouldn't bank on the weather improving'). In writing, 'rely on' is the most neutral choice for both formal and informal contexts. Example: 'You can rely on the bus being on time' (neutral expectation) vs 'You can count on Marta to bring dessert' (personal confidence) vs 'I wouldn't bank on getting a refund' (informal warning).

rely oncount on ↗trust ↗bank on

Common collocations

Adverbs

Phrases

  • can rely on
  • could rely on
  • should be able to rely on
  • must be able to rely on

Prepositions

Etymology

LatinOld FrenchEnglish

'Rely' comes from Latin 'religare', meaning 'to bind fast' — from 're-' (back) and 'ligare' (to bind). It entered English through Old French 'relier' (to fasten, attach). Originally it meant physically tying something back, but by the 16th century the meaning had shifted to a sense of trusting dependence, as if two people were bound together by a promise.