hallucination
/həˌluːsɪˈneɪʃn/ (bre, ipa) · /həˌluːsɪˈneɪʃn/ (ame, ipa) · /hə-ˌlü-sə-ˈnā-shən/ (ame, mw)
hallucination — noun
- hallucinationsingular
- hallucinationsplural
1. a sensory event during which a person sees, hears, feels, or smells things with
a sensory event during which a person sees, hears, feels, or smells things with no basis in external reality, typically triggered by a medical condition, mental illness, a high fever, or drug use
Ritu experienced vivid auditory hallucinations after developing a high fever.
auditory / visual / olfactory hallucination — specifying the sensory type
Layla had visual hallucinations of people not there while awake for two weeks.
The doctors confirmed that the hallucinations were caused by a reaction to the new medication.
Yan's grandfather was diagnosed with a condition that triggers frequent olfactory hallucinations.
After the surgery, Théo mentioned that the hallucinations had completely stopped.
- delusion
A delusion is a fixed false belief (e.g., thinking you are famous), not a sensory experience. Delusions involve thoughts, not senses.
- mirage
A mirage is a visual illusion caused by atmospheric conditions (e.g., water on a hot road), not a medical symptom.
- apparition
Apparition suggests a ghostly or supernatural vision, whereas hallucination is a medical or neurological term.
用法筆記
Often modified by a sensory adjective (auditory, visual, olfactory, tactile) to specify which sense is affected. The uncountable form (e.g., 'suffers from hallucination') is less common than the countable form ('had hallucinations').
常見錯誤
2. the specific thing that someone sees, hears, or feels during a hallucination, ev
the specific thing that someone sees, hears, or feels during a hallucination, even though it has no real existence outside their own mind
One hallucination Dewi reported was a large spider crawling across her shoulder.
hallucination of + [noun] — describing the perceived object
Eli kept insisting the person in the corner of the room was not a hallucination.
The hallucination of a burning smell made the nurses check every room for a fire.
Rodrigo described the hallucination as a bright light that cast shadows on the wall.
文法句型
hallucination of + noun
用法筆記
Use this sense when referring to what the person actually perceived (the content of the hallucination), as opposed to the experience itself. Typically takes an 'of'-phrase (e.g., 'a hallucination of a face').
3. an incorrect statement or fabricated detail that an artificial intelligence syst
an incorrect statement or fabricated detail that an artificial intelligence system creates and presents as if it were reliable, often sounding convincing despite being untrue
The chatbot produced a hallucination when it claimed a famous scientist was still alive.
AI system + produce + hallucination — verb-noun collocation in computing
Rachel deleted the article after discovering it contained several serious hallucinations.
Several AI hallucinations on the forum gave users incorrect medical advice about dosages.
Christopher showed the class an example of an AI hallucination involving a fake historical event.
- fabrication
Fabrication is more general and does not imply AI; a person or a system can fabricate information.
- confabulation
In AI research, confabulation is sometimes used synonymously with hallucination, but hallucination is far more common in non-specialist writing.
- fact
A fact is verified and true; the opposite of a hallucinated piece of information.
文法句型
produce / generate + hallucination
用法筆記
In computing contexts, hallucination refers specifically to incorrect AI-generated output; do not use the medical meaning (senses 1-2) when discussing technology. The countable form ('three hallucinations') is common when referring to individual errors.
常見錯誤
4. the general tendency or phenomenon of artificial intelligence systems producing
the general tendency or phenomenon of artificial intelligence systems producing false or misleading information, considered as a technical problem that researchers try to solve
AI hallucination remains one of the biggest challenges for developers of language models.
AI hallucination + remains / is — subject pattern in academic contexts
Tunde's research paper explores why hallucination occurs in machine translation systems.
hallucination + occurs in / happens in — describing where the phenomenon appears
The company invested heavily in reducing hallucination before launching their medical chatbot.
Selim warned that hallucination could cause serious harm if it affects automated medical diagnoses.
- AI confabulation
A more technical synonym used in academic papers; less common in general technology journalism.
- model error
A broader term that covers any type of mistake an AI makes, not just fabricated content.
- factual accuracy
Factual accuracy is the opposite property — the quality of being correct and true.
用法筆記
This uncountable sense describes the phenomenon as a whole ('reduce hallucination'), rather than individual errors. It is used in technical discussions about AI reliability, safety, and model improvement. Distinguish from sense 3, which refers to a specific false output.
5. an idea about a situation, a person, or a possibility that has no basis in fact
an idea about a situation, a person, or a possibility that has no basis in fact and is held despite a clear lack of supporting evidence, often because the person wants or fears it to be true
The CEO's belief that the firm could not fail was a dangerous hallucination.
hallucination that + clause — specifying the false belief content
Ada dismissed the idea that money alone buys happiness as a comfortable but false hallucination.
Obi lived under the hallucination that his old friends all wanted to harm him.
The politician's speech was built on the hallucination that problems could be solved overnight.
- delusion
Delusion is the more common word for a fixed false belief. Hallucination (sense 5) is more poetic or dramatic.
- fantasy
Fantasy is usually a pleasant imagined scenario that the person knows is not real; a hallucination in this sense is believed to be true.
- misconception
Misconception is a milder, more neutral term for an incorrect understanding.
文法句型
hallucination that + clause
用法筆記
This figurative sense is literary or formal. Unlike sense 1, it involves no sensory perception — only a false belief or expectation. For a false belief that is more rigid and resistant to evidence, use 'delusion' instead.