{{Short description|Being seen by someone or something}} {{refimprove|date=November 2025}} {{Use dmy dates|date=November 2025}} In general, '''detection''' is the action of accessing information without specific cooperation from or with the sender; it is "the fact of noticing or discovering something".<ref name=DicDef>{{cite web|url=https://dictionary.cambridge.org/us/dictionary/english/detection|title=detection; noun|website=Cambridge University Dictionary |access-date=25 November 2025}}</ref>
In the history of [[radio]] communications, the term "[[detector (radio)|detector]]" was first used for a device that detected the simple presence or absence of a radio [[signal (electronics)|signal]], since all communications were in [[Morse code]]. The term is still in use today to describe a component that extracts a particular signal from all of the [[electromagnetic radiation|electromagnetic waves]] present. Detection is usually based on the [[frequency]] of the [[carrier signal]], as in the familiar frequencies of [[radio broadcasting]], but it may also involve filtering a faint signal from [[noise]], as in [[radio astronomy]], or reconstructing a hidden signal, as in [[steganography]].
In [[optoelectronics]], "detection" means converting a received optical input to an electrical output. For example, the light signal received through an [[optical fiber]] is converted to an electrical signal in a detector such as a [[photodiode]].
In [[steganography]], attempts to detect hidden signals in suspected carrier material is referred to as [[steganalysis]]. Steganalysis has an interesting difference from most other types of detection, in that it can often only determine the [[probability]] that a hidden message exists; this is in contrast to the detection of signals which are simply [[encryption|encrypted]], as the [[ciphertext]] can often be identified with certainty, even if it cannot be decoded.
In the [[military]], detection refers to the special discipline of [[reconnaissance]] with the aim to recognize the presence of an object in a location or ambiance, either literally (for example, enemy forces massing on the border) or by extension (as in a defense system or [[computer system]]).<ref>{{cite web|website=United States Military (Department of Defense)|title=Enhanced Maritime Biological Detection System Provides Biodefense Capabilities for Sailors|url=https://www.army.mil/article/289197/enhanced_maritime_biological_detection_system_provides_biodefense_capability_for_sailors_in_near_real_time|access-date=25 November 2025}}</ref>
In [[medicine]], medical devices can provide detection for medical conditions, such as heart conditions by a [[stethoscope]], or the detection of seizures in premature babies.<ref>{{cite web|url=https://www.medtechdive.com/news/ceribell-clearance-seizure-detection-neonates/806376/|website=MedTechDrive|title=Ceribell wins FDA clearance for seizure-detection algorithm in neonates|date=25 November 2025|access-date=25 November 2025|first=Nick Paul|last=Taylor}}</ref>
Finally, the art of detection, also known as ''following clues'', is the work of a [[detective]] in attempting to reconstruct a sequence of events by identifying the relevant information in a situation. In [[law enforcement]], it is "the fact of the police discovering information about crimes".<ref name=DicDef />
==See also== * [[Detection dog]] * [[Object detection]] * [[Signal detection theory]]
==References== {{reflist}}
[[Category:Radio communications]] [[Category:Wireless locating]]