reliability

reliability — noun

1. how trustworthy or dependable someone or something is, shown by working or behav

1.nounB2
Definition

how trustworthy or dependable someone or something is, shown by working or behaving as expected so that people can trust them.

Example

Maja's reliability at work earned her a promotion after only one year.

possessive + reliability + prepositional phrase

The reliability of online reviews is hard to judge when anyone can post fake comments.

the reliability of [noun phrase] as subject

Common collocations
  • prove one's reliability
  • question the reliability of
  • reputation for reliability
  • reliability as a [role]
Synonyms
  • trustworthiness

    very close in meaning; emphasises moral character and honesty more than performance

  • dependability

    interchangeable in most contexts; slightly more common for describing people than machines

  • credibility

    focuses on whether information or a claim can be believed; does not apply to people's work habits

Antonyms
  • unreliability

    direct opposite; describes someone or something that cannot be trusted

  • dishonesty

    narrower — focuses on lying rather than general dependability

Grammar Patterns

the reliability of [noun phrase]

[possessive] reliability as [noun]

Usage Note

Often preceded by a possessive or 'the reliability of' to specify whose or what reliability is being discussed.

Common Mistakes

I trust his reliable.
I trust his reliability.
'reliability' is a noun, not an adjective; use it after a possessive.

2. how well a machine, product, or method keeps working correctly over a long time,

2.nounB2
Definition

how well a machine, product, or method keeps working correctly over a long time, avoiding failure or producing different results.

Example

Engineers tested the bridge's reliability by running heavy trucks across it daily for two months.

The lab measured the new battery's reliability by charging and discharging it five hundred times.

measured [noun]'s reliability by [gerund]

Common collocations
  • long-term reliability
  • prove the reliability of
  • reliability of [equipment]
  • test for reliability
Synonyms
  • durability

    focuses on physical strength and resistance to wear; does not cover consistency of results

  • consistency

    emphasises producing the same output each time; common in scientific and manufacturing contexts

  • stability

    implies the system does not change or fluctuate; often used for networks, software, and emotions

Antonyms
  • unreliability

    direct opposite; frequent breakdowns or inconsistent results

  • inconsistency

    focuses on varying results rather than outright failure

Grammar Patterns

the reliability of [machine/product]

[noun] + reliability

long-term reliability

Usage Note

Common with nouns for equipment (engine, battery, network) and scientific methods (test, measurement, result). Not used for people's character in this sense.

Common Mistakes

The car has high reliable.
The car has high reliability.
'reliable' is an adjective; 'reliability' is the noun form.

Word family

Synonym discussion

Sense: noun/1

All four words describe a quality that makes someone or something worthy of confidence, but they differ in scope. Trustworthiness emphasises honesty and moral character — it is the best word when describing a person's integrity. Dependability overlaps strongly with reliability but leans slightly more toward everyday, practical contexts: a dependable car starts every morning, while a reliable car is trusted to perform well overall. Credibility is narrower, applying mainly to information, sources, or claims — a news outlet loses credibility, not dependability. Consistency, which spans both senses, highlights the absence of variation: a consistent employee produces the same high-quality work each time, and a consistent test gives the same results on repeated trials. For describing a person you can count on in general, dependability and reliability are the closest matches; use trustworthiness when moral character is central, and credibility when discussing information or authority.

trustworthinessdependabilitycredibility ↗consistency ↗

Common collocations

Nouns

Adverbs

Phrases

  • track record of reliability
  • a reputation for reliability
  • the reliability of [something]

Prepositions

Etymology

LatinOld FrenchEnglish

Reliability comes from the verb 'rely', which entered English from Old French 'relier' (to fasten or bind together), tracing further back to Latin 'religare' — 're-' (back) + 'ligare' (to bind). The '-able' suffix turned it into an adjective meaning 'that can be bound or counted on', and '-ity' made it into a noun describing the state of being reliable. The word gained common use in the 1800s alongside the growth of industry and engineering, where the need to describe machines and systems that could be trusted became important.