mentally ill: meaning, definition, pronunciation and examples
Medium-HighFormal, Medical/Legal, sometimes Informal (though increasingly considered dated/impersonal)
Quick answer
What does “mentally ill” mean?
Suffering from a condition that affects a person's thinking, feeling, mood, or behaviour, such as depression, anxiety, or schizophrenia.
Audio
Pronunciation
Definition
Meaning and Definition
Suffering from a condition that affects a person's thinking, feeling, mood, or behaviour, such as depression, anxiety, or schizophrenia.
A general term for having a psychiatric disorder or mental health condition. It can range from mild, temporary conditions to severe, lifelong disorders. In contemporary usage, it is often replaced by more specific or person-first language (e.g., 'has a mental illness').
Dialectal Variation
British vs American Usage
Differences
No significant structural differences. Both varieties use the term. In formal/public contexts, both UK and US styles increasingly recommend person-first language.
Connotations
In both varieties, the term can carry a stigma or sound clinical/impersonal. It is more likely to be found in official reports, legal contexts, or historical texts than in contemporary therapeutic or person-centred communication.
Frequency
Frequency is decreasing in both varieties in favour of more specific or sensitive phrasing, but it remains common in legal, journalistic, and certain academic contexts.
Grammar
How to Use “mentally ill” in a Sentence
to be mentally illto be considered mentally illto be diagnosed as mentally illto care for the mentally ill (as a nominalised group)Vocabulary
Collocations
Examples
Examples of “mentally ill” in a Sentence
verb
British English
- (No direct verb form. Use phrases like) He was sectioned under the Mental Health Act.
- She was diagnosed with a mental illness.
American English
- (No direct verb form. Use phrases like) He was committed to a psychiatric facility.
- She was treated for a mental disorder.
adverb
British English
- (Not applicable. 'Mentally' is already an adverb modifying 'ill').
American English
- (Not applicable. 'Mentally' is already an adverb modifying 'ill').
adjective
British English
- She was found to be mentally ill and unfit to stand trial.
- Providing adequate housing for mentally ill individuals is a challenge.
American English
- The defendant was ruled mentally ill by the court.
- Access to care for mentally ill veterans has improved.
Usage
Meaning in Context
Business
Rare, except in HR contexts discussing accommodations or leave: 'The policy covers extended leave for employees who become mentally ill.'
Academic
Used in sociological, legal, or historical studies, but clinical psychology/psychiatry prefers specific diagnoses: 'Historical attitudes toward the mentally ill were often punitive.'
Everyday
Decreasingly common in casual conversation due to stigma. More likely: 'He has depression' or 'She's struggling with her mental health.'
Technical
Used in legal statutes and some public health reporting as a broad category. Clinical assessments avoid it for specific DSM-5/ICD-11 diagnoses.
Vocabulary
Synonyms of “mentally ill”
Strong
Neutral
Weak
Vocabulary
Antonyms of “mentally ill”
Watch out
Common Mistakes When Using “mentally ill”
- Using it as a noun to refer to a person (e.g., 'He is a mentally ill') – it's an adjective phrase. Correct: 'He is mentally ill' or 'He is a mentally ill person.'
- Using it to describe temporary stress or sadness ('I'm so mentally ill about this exam'), which trivialises serious conditions.
FAQ
Frequently Asked Questions
It can be, depending on context. While it is a standard clinical and legal term, it is broad and can define a person by their illness. Many prefer person-first language like 'a person with a mental illness' or specifying the condition (e.g., 'has bipolar disorder').
'Mentally ill' refers to psychiatric conditions affecting mood, thinking, or behaviour (e.g., depression, schizophrenia). 'Mentally disabled' (or 'intellectually disabled') refers to significantly impaired cognitive functioning and learning abilities, often present from childhood.
Using it as a noun to label a person ('the mentally ill') is grammatically possible as a nominalised adjective but is increasingly avoided in sensitive language. It's better to say 'people with mental illnesses' or 'mentally ill people.'
Not for the phrase itself. Formal diagnoses are made using specific criteria from manuals like the DSM-5 or ICD-11 for disorders such as Major Depressive Disorder or Schizophrenia. 'Mentally ill' is a non-specific umbrella term covering these conditions.
Suffering from a condition that affects a person's thinking, feeling, mood, or behaviour, such as depression, anxiety, or schizophrenia.
Mentally ill: in British English it is pronounced /ˈmen.təl.i ɪl/, and in American English it is pronounced /ˈmen.t̬əl.i ɪl/. Tap the audio buttons above to hear it.
Phrases
Idioms & Phrases
- “Not of sound mind and body (legal)”
- “Not in one's right mind (informal, not equivalent)”
Learning
Memory Aids
Mnemonic
Think: MENTAL + ILL. The MIND (mental) is unwell (ill), not functioning in a healthy way.
Conceptual Metaphor
MENTAL ILLNESS IS PHYSICAL ILLNESS (implies a medical condition requiring treatment, not a character flaw).
Practice
Quiz
Which of the following is the most sensitive and modern alternative to 'He is mentally ill'?