Vocabulary C1 6 min read Updated 15 June 2026

Quick Answer

Credible describes the thing being believed: a claim, witness, threat, or explanation that is believable and deserves trust (a credible witness, a credible threat). Credulous describes the believer: a person who is too willing to accept things as true without proof — in other words, gullible (a credulous investor was fooled). The simplest test: a credulous person believes things that are not credible.

Credible and credulous both come from the Latin credere, “to believe”, which is why they look so similar. But they sit on opposite ends of the act of believing. One describes the object of belief (is it worth believing?), and the other describes the person doing the believing (do they believe too easily?). Getting these mixed up can reverse your meaning entirely, so this pair is well worth mastering at C1 level.

At a Glance: Credible vs Credulous

WordPronunciationMeaningWhat it describes
credible /ˈkrɛdɪbl/ believable; convincing; able to be trusted or believed The thing or person being believed (a claim, witness, threat)
credulous /ˈkrɛdjʊləs/ too ready to believe things; gullible; naive The believer — a person who believes too easily

Using “Credible”

Credible /ˈkrɛdɪbl/ is an adjective meaning believable or convincing. If something is credible, it is worth believing because it is plausible, well supported, or comes from a trustworthy source.

Definition

Able to be believed; convincing; deserving of trust. It can describe statements, evidence, threats, stories, and explanations, and it can also describe people who come across as trustworthy or competent (a credible witness, a credible candidate). The related noun is credibility (the quality of being believed or trusted).

When to use it

  • Describing a claim, story, or explanation that is believable
  • Describing a person, witness, or source seen as trustworthy or reliable
  • Describing a threat or risk that is taken seriously: a credible threat
  • Describing a candidate or alternative that is taken seriously: a credible challenger
  • In the noun form credibility: the report damaged her credibility

The defence could not produce a single credible witness.

Police said the bomb threat was credible and evacuated the building.

She gave a perfectly credible explanation for why she was late.

For the first time, the opposition has a credible chance of winning.

The scandal destroyed the minister’s credibility overnight.

His story was just credible enough that we believed him.

Key Pattern

credible + noun: a credible witness, a credible threat, a credible alternative
be + credible: Her account is credible. / The figures are not credible.
noun form: credibility = the quality of being believed or trusted

Using “Credulous”

Credulous /ˈkrɛdjʊləs/ is an adjective meaning too ready to believe things. A credulous person accepts claims without question and is easily fooled. It is roughly a synonym of gullible and carries a mildly negative, critical tone.

Definition

Having or showing too great a readiness to believe things; gullible; naive. It almost always describes a person (or their behaviour, audience, or attitude), never a claim or piece of evidence. The related noun is credulity (a willingness to believe too easily).

When to use it

  • Describing a person who believes things too easily: a credulous customer
  • Describing an audience or public that is easily taken in: credulous fans
  • Describing a naive attitude or reaction: a credulous acceptance of the rumour
  • When something exploits people’s readiness to believe: scams that prey on the credulous
  • In the noun form credulity: the con artist relied on his victims’ credulity

A credulous investor handed over his savings to the fraudster.

The healer made a fortune from credulous patients.

Only the most credulous reader would take that headline at face value.

She is far too credulous — she believes everything she reads online.

The advertisement was designed to appeal to credulous buyers.

His credulity made him an easy target for con artists.

Key Pattern

credulous + person noun: a credulous investor, credulous fans, a credulous public
be + credulous: He is too credulous. / Don’t be so credulous.
noun form: credulity = a readiness to believe too easily

The Key Difference: Thing Believed vs the Believer

The single distinction to remember is who or what each word describes. Credible describes the thing or person being believed — it answers the question “is this worth believing?” Credulous describes the person doing the believing — it answers the question “do they believe too easily?”

Crucially, the two are linked: a credulous person is exactly the kind of person who believes things that are not credible. A con artist tells a story that is not credible, and only a credulous listener falls for it. Once you fix this relationship in your mind, the pair almost never causes trouble again.

Describing the claim (credible):

The witness gave a credible account of the accident.

Describing the believer (credulous):

The credulous jury believed the witness without question.

Common Mistakes

He gave a credulous account of what happened.

He gave a credible account of what happened. (the account is believable, so it is credible; an account cannot be credulous)

Even credible people fall for these scams.

Even credulous people fall for these scams. (the people believe too easily, so they are credulous)

The evidence was credulous and convincing.

The evidence was credible and convincing. (evidence can be believable, but it cannot be gullible)

I was incredible that he had lied to me.

I was incredulous that he had lied to me. (a person who cannot believe something is incredulous, not incredible)

Related Words: Credence, Credulity, and the “In-” Forms

This word family is large, and a few close relatives are worth knowing so you can keep them apart.

Credence

Credence is a noun meaning belief in, or acceptance of, something as true. It usually appears in the phrase give credence to (= to believe or treat as true).

I would not give credence to a rumour like that.

The new evidence lends credence to her theory.

Credulity

Credulity is the noun form of credulous: a readiness to believe too easily. Note the common idiom to stretch credulity (= to be almost too far-fetched to believe).

The plot of the film really stretches credulity.

Fraudsters thrive on the credulity of their victims.

Credible vs Incredible

Incredible is the opposite of credible: literally “not believable”. In everyday English it has weakened to mean amazing or extraordinary, but its core sense is “hard to believe”.

His excuse was simply incredible — nobody believed a word. (not believable)

The view from the summit was incredible. (amazing)

Credulous vs Incredulous

Incredulous is the opposite of credulous: unwilling or unable to believe something, sceptical, showing disbelief. An incredulous person is the opposite of a gullible one.

She gave me an incredulous look when I said I had quit my job.

He was incredulous at the news and demanded proof.

Watch Out

Do not confuse incredible (describes the unbelievable thing) with incredulous (describes the disbelieving person). The same thing/person split that separates credible from credulous applies to their “in-” forms.

Memory Tip

Link credulous to gullible — both describe a foolish, easily fooled person, and both have that “-l-ous / -lible” ending. By contrast, credible shares its ending with believable and sensible — reliable adjectives about the thing itself. So: credulous people believe things that are not credible. If the word describes a person who is too trusting, it is credulous; if it describes something worth believing, it is credible.

Frequently Asked Questions

What is the difference between credible and credulous?
Credible describes the thing or person being believed: a claim, witness, threat, or explanation that is believable and deserves trust (a credible witness, a credible threat). Credulous describes the believer: a person who is too ready to believe things and is easily fooled, which is close in meaning to gullible (a credulous investor was tricked). The simplest way to keep them apart is to remember that a credulous person believes things that are not credible.
Does credible or credulous describe a person?
Both can describe a person, but in different ways. Credible describes a person who is trustworthy and worth believing — a credible witness, a credible candidate. Credulous describes a person who believes too easily and is naive — a credulous customer, a credulous public. So a credible person is reliable, while a credulous person is gullible. Importantly, only credible can also describe non-people such as claims, evidence, or threats; credulous is almost always reserved for people or their attitudes.
How do you pronounce credible and credulous?
Credible is pronounced /ˈkrɛdɪbl/ — three syllables, KRED-ib-uhl, with the stress on the first syllable. Credulous is pronounced /ˈkrɛdjʊləs/ — three syllables, KRED-yuu-luhs, also stressed on the first syllable. The key spoken difference is in the middle: credible has a short "ib" sound, while credulous has a "yuu" sound, like the start of "use". Both begin with the same "kred" element from the Latin credere, meaning "to believe".
Is credulous the same as gullible?
They are very close synonyms. Both describe a person who is too ready to believe things and is easily deceived. Credulous is slightly more formal and is common in written or academic English, while gullible is more everyday and conversational. There is a subtle shade of difference: credulous emphasises a general willingness to believe, whereas gullible emphasises being easy to trick. In most contexts, however, you could swap one for the other: a credulous customer and a gullible customer mean much the same thing.
What is the noun form of credible and credulous?
The noun form of credible is credibility, meaning the quality of being believed or trusted: the scandal damaged her credibility. The noun form of credulous is credulity, meaning a readiness to believe too easily: the con artist relied on his victims' credulity. There is also a third related noun, credence, which means belief in or acceptance of something as true, usually in the phrase give credence to: I would not give credence to that rumour. All three come from the same Latin root, credere, "to believe".
Can a claim or piece of evidence be credulous?
No. A claim, account, story, or piece of evidence can be credible (believable) but never credulous. Credulous describes a person — or, by extension, an audience, public, or attitude — that believes too easily. So you can say a credible account or credible evidence, but if you want to describe how readily someone accepts it, the credulous reader or a credulous audience is correct. Writing "a credulous account" is a common error; the right word for a believable account is credible.
What does "give credence to" mean?
Give credence to something means to believe it or to treat it as true and worthy of acceptance. Credence is a noun meaning belief in, or acceptance of, something as true. For example, I would not give credence to a rumour like that means "I would not believe it". A related phrase is lend credence to, meaning to make something more believable: the new evidence lends credence to her theory. Credence is not used to describe people, only the act of believing or accepting an idea.
What is the difference between incredible and incredulous?
Incredible is the opposite of credible and means "not believable" — though in everyday English it has come to mean amazing or extraordinary: his excuse was incredible (not believable); the view was incredible (amazing). Incredulous is the opposite of credulous and means "unwilling or unable to believe", that is, sceptical or showing disbelief: she gave me an incredulous look. The same thing-versus-person split applies: incredible describes the unbelievable thing, while incredulous describes the disbelieving person.
What does "stretch credulity" mean?
To stretch credulity means to be so far-fetched or unlikely that it is almost too difficult to believe. Credulity here is the noun meaning a readiness to believe, and "stretching" it suggests pushing that readiness to its limit. For example, the plot of the film really stretches credulity means the plot is barely believable. A related expression is "beggar belief", which has a similar meaning. The phrase is useful in formal or critical writing when you want to say something is hard to accept as true.
How can I remember which word is which?
A reliable trick is to link credulous with gullible: both describe a foolish, easily fooled person, and both share a similar "-lous / -lible" ending. By contrast, credible shares its "-ible" ending with believable and sensible, dependable adjectives that describe the thing itself. So a credulous person believes things that are not credible. If the word describes a person who is too trusting, choose credulous; if it describes a claim, threat, or person worth believing, choose credible.

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