Communication

112 — Emergency telephone number 112 (emergency telephone number) 112 is the single emergency number used across the European Union and on GSM mobile networks; it connects callers to police, fire and medical services and is free from most phones.

2-1-1: Community information and referral telephone service 2-1-1 2-1-1 is a three-digit community information and referral number in the United States and Canada connecting callers to local health, social and disaster resources.

9-1-1 — the emergency telephone number 9-1-1 9-1-1 is a dedicated emergency telephone number used in several countries and territories for police, fire, and medical dispatch. This article explains purpose, use, history, and i…

999 (nine-nine-nine): the United Kingdom and Ireland emergency number 9-9-9 999 (nine-nine-nine) is the primary emergency telephone number in the UK and Ireland, connecting callers to police, fire, ambulance and other rescue services. 112 is also accepted…

911 — year, emergency number, and other common meanings 911 911 may denote the year AD 911, the North American emergency telephone number, the September 11 attacks, or other cultural uses such as the Porsche 911. Overview, history, and key…

988 Suicide & Crisis Lifeline A U.S. national network that provides free, confidential 24/7 crisis counseling by phone, text, or chat to people in suicidal distress or emotional crisis.

Å — the Scandinavian letter A with a ring Å Å is a distinct letter in several Nordic alphabets. It represents a rounded back vowel, evolved from Old Norse, and appears in Danish, Norwegian, Swedish and in Finnish names and l…

A (Cyrillic) The Cyrillic letter A (А, а) is the first letter of the Cyrillic script, derived from Greek alpha; it commonly denotes the vowel /a/ and once held the numeric value 1 in early Slav…

Abbreviation: forms, uses, and how it differs from acronyms Abbreviation Overview of abbreviations: definitions, types (initialisms, acronyms, contractions), punctuation and style, common examples, history, and guidelines for clear use.

Abenaki language A member of the Algonquian family spoken historically in northeastern North America. Endangered today, Abenaki includes Eastern and Western varieties and is the focus of active rev…

Abjad: consonant-based writing systems Abjad An abjad is a writing system that principally records consonants; vowels may be omitted or marked separately. Common in Semitic scripts, abjads influenced the development of full a…

Abkhaz language Northwest Caucasian language spoken primarily in Abkhazia (Georgia) and by diasporas in Turkey. Known for a large consonant inventory, complex verbal morphology, and several region…

Abugida (alphasyllabary) Abugida An abugida is a segmental writing system where consonant signs carry an inherent vowel; vowels are written with secondary marks or modifications. Overview, structure, history, exam…

Accent — regional and personal patterns of pronunciation Accent A clear, neutral overview of accents: what they are, how they form, linguistic features, common examples, learning effects, and social perceptions.

Acronym: definition, types, history and usage Acronym A concise reference on acronyms: what they are, how they differ from initialisms, formation rules, history, common examples, pronunciation and style variations.

Acute accent (´): uses, history, and typographic notes Acute accent The acute accent (´) is a common diacritic placed on letters to mark stress, vowel quality, length, or tone across many writing systems using Latin, Greek, and Cyrillic alphabets.

Address (contact identifier and location descriptor) Address An address is an identifier used to locate or contact a person, organization, place, or device; includes postal, electronic and other addressing systems and conventions.

Adyghe language (Adygebze) — Circassian language of the Northwest Caucasus Adyghe language Adyghe (Adygebze) is a Northwest Caucasian (Circassian) language spoken by the Adyghe people in the Republic of Adygea and diasporas. It is known for a large consonant inventory, c…

Afar language (Qafaraf) — an East Cushitic language of the Horn of Africa Afar language Afar (Qafaraf) is an East Cushitic language spoken by the Afar people in Ethiopia, Eritrea and Djibouti. It is closely related to Saho and is used in oral tradition, media and loca…

Affricate (speech sound) Affricate An affricate is a consonant that begins with a stop closure and releases as a fricative; languages contrast affricates by voicing, aspiration and place of articulation.

African-American Vernacular English African-American Vernacular English (AAVE) is a systematic variety of English with distinctive pronunciation, grammar, vocabulary, historical roots in creole and West African conta…

Afrikaans: origin, features, and contemporary role Afrikaans Afrikaans is a West Germanic language that developed at the Cape; this article surveys its origins, structure, varieties, history, and its place in modern Southern Africa.

Afroasiatic languages: overview, branches, history and modern role Afroasiatic languages Afroasiatic is a major language family of North Africa, the Horn, the Sahel and Western Asia, comprising six branches (including Semitic and Berber) and hundreds of languages with…

Aimaq dialect (Persian ethnolect) Aimaq dialect Aimaq is a group of Persian dialects spoken by the Aimaq people in parts of Afghanistan, Iran and Tajikistan. It is an oral regional variety with distinct pronunciation, vocabulary…

Air gap (networking) A security practice that physically isolates a computer or network from untrusted networks to reduce remote attack risk. Common in classified, industrial and critical infrastructur…

Air–Ground Radiotelephone Service Air-ground radiotelephone service Air–ground radiotelephone service is a radio-based method for voice calls between aircraft and land telephone networks, historically used by crew and passengers and evolving into m…

Ajam (Arabic term for non‑Arabic speaker and its historical meanings) Ajam Ajam is an Arabic word historically used for non‑Arabic speakers, often Persians. The term has linguistic, cultural and historical layers, with changing connotations across time an…

Akkadian language (Assyro-Babylonian): history, features, and legacy Akkadian language Akkadian was the earliest attested Semitic language of ancient Mesopotamia, recorded in cuneiform. This article surveys its dialects, writing system, major texts, historical role,…

Alarm (alerting device) Alarm An alarm is a device or system that alerts people to a condition requiring attention, using sound, light, vibration, network messages, or combinations for safety, security, and tim…

Albanian language (Shqip): overview, history, dialects and usage Albanian language Albanian (Shqip) is an Indo-European language forming its own branch. Spoken in Albania, Kosovo and surrounding regions, it has two main dialects, a Latin-based alphabet, and a ric…

Alemannic German (Alemannisch): dialects of Upper German Alemannic German Alemannic German is a group of Upper German dialects spoken across parts of central Europe and a few diaspora communities. This article describes its varieties, history, distributi…

Alice and Bob: Placeholders for Parties in Science and Security Alice and Bob Common placeholder names used to illustrate interactions between parties in cryptography, game theory, physics and related fields; often accompanied by Eve, Mallory, and others.

All your base are belong to us — origin and cultural impact All your base are belong to us A concise account of the phrase “All your base are belong to us”, its origin in Zero Wing, and how a mistranslation became an early internet meme and cultural reference.

Alphabet: systems of written letters and their roles Alphabet An alphabet is a standardized set of letters used to represent spoken language. This article explains what alphabets are, how they differ from other scripts, their history, structu…

Alveolar consonant Consonants articulated with the tongue against or near the alveolar ridge. Covers articulation, common types (stops, nasals, fricatives, laterals, taps), examples, and distinctions…

Amateur radio (ham radio): hobby, technology, and public service Amateur radio Amateur radio, or ham radio, is a licensed hobby and service that uses radio transmitters and receivers for personal communication, technical experimentation, and emergency support…

AMBER Alert (child abduction emergency broadcast system) Amber alert AMBER Alert is a rapid public-warning system for suspected child abductions, created in the United States in 1996 to enlist the public in locating children, suspects, and related v…

American English Variety of English used in the United States, distinguished by regional dialects, pronunciation, vocabulary, spelling conventions, and historical influences shaping its standard an…

American Sign Language (ASL): Overview, History, Grammar, and Use American Sign Language A concise reference on American Sign Language — its origins, linguistic features, geographic distribution, educational role, and fingerspelling conventions.

Amharic language Amharic is a Semitic language of Ethiopia and the second-most spoken Semitic tongue after Arabic. It uses the Ge'ez-derived Fidel script and serves as Ethiopia’s federal working la…

Amplitude modulation (AM): principles, propagation, history, and uses Amplitude modulation Amplitude modulation (AM) is a radio transmission method in which a carrier wave's amplitude is varied to carry sound or data. This article explains how AM works, its history, prop…

Analog signal A continuous-time signal that conveys information by varying a physical quantity; used in audio, video, sensors and control systems and contrasted with digital signals.

Anglicisation: adaptation of foreign names, words and forms into English Anglicisation Anglicisation (anglicization) is the process of adapting non‑English words, names or orthography so they are easier to pronounce, write, or accept in English; includes history and…

Anglo-Frisian languages A concise overview of the Anglo-Frisian subgroup of West Germanic languages, its defining sound changes, historical development, modern varieties, and its place in Germanic classif…

Anglo-Norman language: history, features and legacy Anglo-Norman language Anglo-Norman was the variety of Norman French used by the medieval ruling class in England after 1066. It shaped administration, law and literature and left a lasting imprint on En…

AP: common meanings, origins, and uses AP AP is a two-letter abbreviation with many popular senses — notably the Associated Press, Advanced Placement, access point (Wi‑Fi), accounts payable, and others across media, educat…

Aragonese language (Aragonés) Aragonese language Aragonese is a Romance language spoken in northern Aragon. It has several thousand speakers, shares features with Iberian and Occitan languages, and is the subject of revitalizatio…

Aramaic language — history, script, dialects and modern use Aramaic language Aramaic is an ancient Northwest Semitic language once widespread across the Near East, with a long literary tradition, a distinctive alphabet, and living modern dialects today.