Technology glossary

Contrail Cirrus

Thin, high ice cloud that develops when persistent aircraft contrails spread and lose their original linear shape. Its climate effect varies with location and time, but globally it is considered a net source of warming.

Controlled Lunar Impact

A planned end-of-mission trajectory that deliberately sends a spacecraft or rocket stage into a selected area of the Moon. Operators may use it for disposal or science when the time and location can be predicted and documented.

Controlled Splashdown

A planned descent that places a spacecraft or rocket stage into a defined ocean area while controlling its path, attitude or impact conditions. A controlled splashdown can test guidance and landing systems or dispose of hardware safely, but it does not necessarily mean the vehicle will be recovered or reused.

Controlled-NOT Gate(CNOT)

A two-qubit quantum logic gate in which one qubit controls whether another qubit is flipped.

Coordinated Universal Time(UTC)

Coordinated Universal Time (UTC) is the international reference time scale used for civil timekeeping. GNSS systems maintain their own internal time scales and provide information that allows receivers and timing equipment to relate them to UTC.

COPD Exacerbation

A sudden worsening of chronic obstructive pulmonary disease symptoms beyond normal day-to-day variation. Moderate episodes usually require systemic steroids or antibiotics, while severe episodes commonly require emergency care or hospitalization.

Copy-number variation(CNV)

A copy-number variation is a gain or loss of a DNA segment relative to the usual number of copies. It can affect part of a gene, one or more whole genes, or much larger genomic regions. CNVs may be inherited, arise in an egg or sperm, or occur after conception in only some cells. Their effects range from harmless variation to altered gene dosage and disease risk, depending on size, location and the genes involved.

Copyright Settlement

A negotiated agreement resolving a copyright dispute without a final trial judgment on every legal issue.

Coral Bleaching

A stress response in which corals lose or expel the microscopic algae living in their tissues, causing the colony to turn pale or white. Bleached coral is still alive at first, but prolonged stress raises the risk of starvation, disease and death.

Core-Shell Nanoparticle

A nanoscale particle built from an inner material surrounded by a distinct outer material. Separating the optical or chemical roles of the core and shell lets researchers tune scattering, stability, surface chemistry and compatibility.

Coronagraph

An optical system that suppresses light from a bright star so that much fainter nearby objects can be observed. It uses masks and carefully controlled optics, but residual starlight still limits which planets can be detected.

Coronal Mass Ejection (CME)

A massive eruption of magnetized plasma from the Sun's outer atmosphere, the corona. When an Earth-directed CME strikes the planet's magnetic field, it can trigger geomagnetic storms that produce auroras but can also disrupt power grids, satellites, and radio and GPS signals.

Correlated Color Temperature(CCT)

A lighting metric expressed in kelvins that describes whether a white or near-white light appears warmer and more amber, or cooler and more blue. It is a useful shorthand, but the full spectrum is needed to predict biological effects.

Cortical Organoid

A three-dimensional cluster of stem-cell-derived neural cells that reproduces selected cell types and developmental features of the cerebral cortex without forming a complete brain.

Cortical Synchronization

Coordinated timing of electrical activity across populations of neurons in the cerebral cortex. Strong slow synchronization is characteristic of deep NREM sleep, although it also appears in other brain states and is not by itself proof of sleep.

Cosmic Redshift

The shift of light from distant astronomical objects toward longer, redder wavelengths, commonly caused by the expansion of the universe stretching the light during its journey. Astronomers use redshift to infer cosmic distance, expansion history, and the epoch from which the light originated.

Cost-Effectiveness Analysis

A method that compares the health outcomes and costs of different medical interventions.

Counter-Screening

Counter-screening tests a candidate under deliberately different control conditions to determine whether an apparent positive result reflects the intended target or an unwanted interaction with another target or the measurement system. It helps reject misleading hits, but passing one counter-screen does not establish universal selectivity.

Counterintelligence

The work of detecting, understanding and disrupting intelligence activity conducted by foreign states or other hostile actors. In technology protection it can combine security investigations, insider-risk controls, cyber defence and cooperation with law enforcement, while remaining subject to legal limits and oversight.

Country-of-Origin Claim

A statement indicating where a product was manufactured, assembled or substantially transformed. Legal requirements vary by jurisdiction and by how qualified the wording is, so a marketing phrase may need evidence about components, processing and final assembly.

Covered List

A government list of communications equipment and services considered to pose an unacceptable national-security risk.

Covert channel

An unintended communication path that transfers information through a shared resource rather than an approved interface. Examples include encoding data in processor-cache timing, storage activity or competition for computing resources.

Crater Ejecta

Rock, dust and fragmented material thrown outward when an object strikes a planetary surface and excavates a crater. Ejecta can blanket nearby terrain, bury older landforms and make geological mapping more difficult.

Credential Abuse

The unauthorized use of a valid username, password, token or key to enter a system or act as a legitimate account. Because the credential may pass normal authentication, detection often depends on unusual behavior, location, device or access patterns.

Credential Surrogation

A design in which a trusted service uses a password or token on behalf of an application without revealing the original credential to it.

Crew Resource Management(CRM)

Training and operating practices that help flight crews use communication, leadership, teamwork, situational awareness, and decision-making to manage threats and errors.

CRISPR(CRISPR)

CRISPR is a natural defense system found in bacteria and archaea that stores short pieces of genetic material from past infections and uses them to recognize matching invaders. Scientists adapted this system into a programmable platform for targeting specific DNA sequences in research, diagnostics, and gene editing.

CRISPR-Cas9(CRISPR-Cas9)

CRISPR-Cas9 is a gene-editing system that combines a programmable guide RNA with the Cas9 enzyme. The guide RNA directs Cas9 to a chosen DNA sequence, where Cas9 cuts the DNA so the cell’s repair machinery can disable a gene or introduce a planned genetic change.

Cross-Border Censorship

The suppression, restriction, or manipulation of information in one country through pressure, legal demands, technical controls, or platform policies that reach across national borders. It may target media, online speech, diaspora communities, or services operating internationally.

Cross-Origin Access

Access by one website or embedded context to data or actions belonging to a different web origin.