intruder

USAGE SUMMARY

The phrase "intruder" is correct and usable in written English. You can use it to refer to someone who enters a place without permission, often implying a sense of threat or violation. Example: "The alarm went off when the intruder entered the house." Alternative expressions include "trespasser" and "unauthorized person."

✓ Grammatically correct

News & Media

Encyclopedias

Science

Academia

Human-verified examples from authoritative sources

Exact Expressions

60 human-written examples

The reasoning is that if there was a human intruder then the dog would bark and if a dog intruded then the cat would have howled.

SEP

Three women who work at a hair care shop testified that they heard Kaarma say that same day that he had been waiting up nights to shoot an intruder.

The Guardian

The United Arab Emirates' state news agency says the Gulf nation has dispatched a medical plane to bring three sisters home, nearly 10 months after they were attacked by a hammer-wielding intruder in their luxury London hotel room.

The Guardian

Photograph: Penny Bradfield/Guardian Australia A (presumably well-refreshed) intruder crashes the stage after Tony Abbott's victory speech.

The Guardian

Scotland Yard is reviewing why officers were not sent to investigate an intruder alarm set off there shortly after midnight on the Friday.

The Guardian

It is a situation that makes the original wall look like the intruder, a piece of Disneyfied old London copied and pasted from elsewhere.

The Guardian - Arts

Kaarma insists he feared for his life and didn't know if the intruder was armed.

The Guardian

One of her most recent projects was L'intrus (The Intruder), a film about the heart transplant of philosopher Jean-Luc Nancy.

The Guardian - Film

Toby Bruce, the leader of the scientific team, said on Twitter that the intruder had broken into the site, spread wheat seed on some plots, and cut the tops off plants on another.

The Guardian

Photograph: Marianna Massey/Getty Images Facebook Twitter Google plus Share Share this post Facebook Twitter Google plus close 11.19pm AEST14 19 A (presumably well-refreshed) intruder crashes the stage after Tony Abbott's victory speech.

The Guardian

When a mysterious and anonymous intruder invades their six-way Skype session and starts planting venomous private information into their forum, the teenagers first stand together, then fall apart, then turn on one another.

The Guardian - Film

Expert writing Tips

Best practice

In biological contexts, employ "intruder" to describe pathogens or foreign cells that trigger an immune response.

Common error

Avoid the common tautology of saying "unauthorized intruder". Since the definition of an "intruder" inherently implies lack of authorization, the adjective is redundant and can be removed to make your writing more concise.

Linguistic Context

The word "intruder" is a count noun derived from the verb 'intrude'. It typically functions as the head of a noun phrase, acting as a subject or direct object to identify a person, animal or entity that has crossed a boundary without permission. According to Ludwig, it is the standard term for describing violations of domestic, biological and digital spaces.

Expression frequency: Very common

Frequent in

News & Media

77%

Encyclopedias

8%

Science

5%

Less common in

Social Media

4%

Wiki

3%

Formal & Business

3%

Ludwig's WRAP-UP

In conclusion, "intruder" is a highly versatile and essential noun in English for describing unauthorized entry across various domains. Ludwig AI samples show that while it is most commonly associated with criminal or security contexts—such as home invasions or alarm triggers—it is equally significant in biological and academic discourse. Whether referring to a "trespasser" in a house, an "interloper" in a social circle or a foreign cell in the body, the term consistently conveys a breach of established boundaries. Its usage is universally accepted as correct and its formal register makes it suitable for professional, journalistic and scientific writing alike. Writers should be mindful of its inherent meaning to avoid redundant modifiers like 'unauthorized' and choose from its list of synonyms when more specific legal or social connotations are required.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

trespasser

Focuses on the legal aspect of entering land or property without the owner's permission.

interloper

Implies someone who becomes involved in a place or situation where they are not wanted or are considered not to belong.

infiltrator

Implies entering an organization or place secretly in order to acquire information or cause damage.

invader

Suggests a larger scale or more aggressive entry, often by force or for the purpose of conquest.

prowler

Specifically refers to someone moving stealthily around a place, usually with criminal intent.

uninvited guest

A more polite or euphemistic way to describe someone present without permission.

gatecrasher

A more informal term for someone who attends a social event without an invitation.

encroacher

Used when someone gradually or stealthily takes over someone else's space, rights or property.

burglar

Adds the specific intent of theft to the act of unauthorized entry.

adversary

Focuses on the hostile relationship rather than the act of entry itself.

FAQs

How to use "intruder" in a sentence?

You can use it to describe someone entering a property illegally, such as: "The security system was triggered when the "intruder" broke the window". It is also used in science, for example: "The immune system works to destroy any foreign "invader" or "intruder" detected in the body".

What is the difference between an "intruder" and a "burglar"?

An "intruder" is simply anyone who enters without permission, whereas a "burglar" enters specifically to commit a crime, usually theft. All burglars are intruders, but not all intruders are burglars.

What can I say instead of "intruder"?

Depending on the context, you can use alternatives like "trespasser", "interloper" or "uninvited guest".

Is "intruder" used only for people?

No, it is frequently used for animals, such as a dog or spider entering a territory, as well as for digital threats like a "hacker" or a "virus".