MDN Web Docs Glossary: Definitions of Web-related terms

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Quaternion
A quaternion is the quotient of two 3D vectors and is used in 3D graphics and in accelerometer-based sensors to represent orientation or rotational data.

Web technologies contain long lists of jargon and abbreviations that are used in documentation and coding. This glossary provides definitions of words and abbreviations you need to know to successfully understand and build for the web.

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  1. MDN Web Docs Glossary
    1. 404
    2. 502
    3. AJAX
    4. ALPN
    5. API
    6. ARIA
    7. ARPA
    8. ASCII
    9. ATAG
    10. Abstraction
    11. Accessibility
    12. Accessibility tree (AOM)
    13. Adobe Flash
    14. Algorithm
    15. Alignment container
    16. Alignment subject
    17. Alpha (alpha channel)
    18. Apple Safari
    19. Application Context
    20. Argument
    21. Arpanet
    22. Array
    23. Asynchronous
    24. Attribute
    25. Bandwidth
    26. Base64
    27. Baseline
    28. BiDi
    29. BigInt
    30. Blink
    31. Block
    32. Block cipher mode of operation
    33. Boolean
    34. Boot2Gecko
    35. Bootstrap
    36. Bounding Box
    37. Breadcrumb
    38. Brotli
    39. Browser
    40. Browsing context
    41. Bézier curve
    42. CDN
    43. CIA
    44. CMS
    45. CORS
    46. CORS-safelisted request header
    47. CORS-safelisted response header
    48. CRLF
    49. CRUD
    50. CSP
    51. CSRF
    52. CSS
    53. CSS Object Model (CSSOM)
    54. CSS pixel
    55. CSS preprocessor
    56. Cache
    57. Cacheable
    58. CalDAV
    59. Call stack
    60. Callback function
    61. Canonical order
    62. Canvas
    63. Card sorting
    64. CardDAV
    65. Certificate authority
    66. Certified
    67. Challenge-response authentication
    68. Character
    69. Character encoding
    70. Character set
    71. Chrome
    72. Cipher
    73. Cipher suite
    74. Ciphertext
    75. Class
    76. Client hints
    77. Closure
    78. Code splitting
    79. Codec
    80. Compile
    81. Compile time
    82. Computer Programming
    83. Conditional
    84. Constant
    85. Constructor
    86. Continuous Media
    87. Control flow
    88. Cookie
    89. Copyleft
    90. Crawler
    91. Cross Axis
    92. Cross-site scripting
    93. Cryptanalysis
    94. Cryptographic hash function
    95. Cryptography
    96. DHTML
    97. DMZ
    98. DNS
    99. DOM (Document Object Model)
    100. DTLS (Datagram Transport Layer Security)
    101. DTMF (Dual-Tone Multi-Frequency signaling)
    102. Data structure
    103. Decryption
    104. Denial of Service
    105. Descriptor (CSS)
    106. Deserialization
    107. Developer Tools
    108. Digest
    109. Digital certificate
    110. Distributed Denial of Service
    111. DoS attack
    112. Doctype
    113. Document directive
    114. Domain
    115. Domain name
    116. Domain sharding
    117. Dominator
    118. Dynamic programming language
    119. Dynamic typing
    120. ECMA
    121. ECMAScript
    122. Effective connection type
    123. Element
    124. Empty element
    125. Encapsulation
    126. Encryption
    127. Endianness
    128. Engine
    129. Entity
    130. Entity header
    131. Event
    132. Exception
    133. Expando
    134. FTP
    135. FTU
    136. Fallback alignment
    137. Falsy
    138. Favicon
    139. Fetch directive
    140. Fetch metadata request header
    141. Firefox OS
    142. First CPU idle
    143. First Meaningful Paint
    144. First contentful paint
    145. First input delay
    146. First interactive
    147. First paint
    148. First-class Function
    149. Flex
    150. Flex Container
    151. Flex Item
    152. Flexbox
    153. Forbidden header name
    154. Forbidden response header name
    155. Fork
    156. Fragmentainer
    157. Function
    158. Fuzz testing
    159. GIF
    160. GIJ
    161. GPL
    162. GPU
    163. Gaia
    164. Garbage collection
    165. Gecko
    166. General header
    167. Git
    168. Global object
    169. Global scope
    170. Global variable
    171. Glyph
    172. Gonk
    173. Google Chrome
    174. Graceful degradation
    175. Grid
    176. Grid Areas
    177. Grid Axis
    178. Grid Cell
    179. Grid Column
    180. Grid Lines
    181. Grid Row
    182. Grid Tracks
    183. Grid container
    184. Guard
    185. Gutters
    186. Gzip compression
    187. HMAC
    188. HPKP
    189. HSTS
    190. HTML
    191. HTML5
    192. HTTP
    193. HTTP header
    194. HTTP/2
    195. HTTP/3
    196. HTTPS
    197. Hash
    198. Head
    199. High-level programming language
    200. Hoisting
    201. Host
    202. Hotlink
    203. Houdini
    204. Hyperlink
    205. Hypertext
    206. I18N
    207. IANA
    208. ICANN
    209. ICE
    210. IDE
    211. IDL
    212. IETF
    213. IIFE
    214. IMAP
    215. IP Address
    216. IPv4
    217. IPv6
    218. IRC
    219. ISO
    220. ISP
    221. ITU
    222. Idempotent
    223. Identifier
    224. Immutable
    225. Index
    226. IndexedDB
    227. Information architecture
    228. Inheritance
    229. Input method editor
    230. Instance
    231. Internationalization
    232. Internet
    233. Intrinsic Size
    234. JPEG
    235. JSON
    236. Jank
    237. Java
    238. JavaScript
    239. Key
    240. Keyword
    241. LGPL
    242. LTR (Left To Right)
    243. Latency
    244. Layout viewport
    245. Lazy load
    246. Ligature
    247. Local scope
    248. Local variable
    249. Locale
    250. Localization
    251. Long task
    252. Loop
    253. Lossless compression
    254. MIME type
    255. MVC
    256. Main Axis
    257. Main thread
    258. MathML
    259. Media
    260. Metadata
    261. Method
    262. Microsoft Edge
    263. Microsoft Internet Explorer
    264. Middleware
    265. MitM
    266. Mixin
    267. Mobile First
    268. Modem
    269. Modern web apps
    270. Modularity
    271. Mozilla Firefox
    272. Mutable
    273. NAT
    274. NNTP
    275. NaN
    276. Namespace
    277. Native
    278. Navigation directive
    279. Netscape Navigator
    280. Network throttling
    281. Node
    282. Node.js
    283. Normative
    284. Null
    285. Nullish value
    286. Number
    287. OOP
    288. OTA
    289. OWASP
    290. Object
    291. Object reference
    292. OpenGL
    293. OpenSSL
    294. Opera Browser
    295. Operand
    296. Operator
    297. Origin
    298. P2P
    299. PAC
    300. PDF
    301. PHP
    302. PNG
    303. POP3
    304. Packet
    305. Page load time
    306. Page prediction
    307. Parameter
    308. Parent object
    309. Parse
    310. Parser
    311. Perceived performance
    312. Percent-encoding
    313. Pixel
    314. Placeholder names
    315. Plaintext
    316. Polyfill
    317. Polymorphism
    318. Port
    319. Prefetch
    320. Preflight request
    321. Prerender
    322. Presto
    323. Primitive
    324. Privileged
    325. Progressive Enhancement
    326. Progressive web apps
    327. Promise
    328. Property
    329. Protocol
    330. Prototype
    331. Prototype-based programming
    332. Proxy server
    333. Pseudo-class
    334. Pseudo-element
    335. Pseudocode
    336. Public-key cryptography
    337. Python
    338. QUIC
    339. Quality values
    340. Quaternion
    341. RAIL
    342. RDF
    343. REST
    344. RGB
    345. RIL
    346. RSS
    347. RTCP (RTP Control Protocol)
    348. RTF
    349. RTL (Right to Left)
    350. RTP (Real-time Transport Protocol) and SRTP (Secure RTP)
    351. RTSP: Real-time streaming protocol
    352. Random Number Generator
    353. Raster image
    354. Real User Monitoring (RUM)
    355. Recursion
    356. Reference
    357. Reflow
    358. Regular expression
    359. Rendering engine
    360. Repo
    361. Reporting directive
    362. Request header
    363. Resource Timing
    364. Response header
    365. Responsive web design
    366. Robots.txt
    367. Round Trip Time (RTT)
    368. Routers
    369. Ruby
    370. SCM
    371. SCTP
    372. SDP
    373. SEO
    374. SGML
    375. SIMD
    376. SISD
    377. SLD
    378. SMPTE (Society of Motion Picture and Television Engineers)
    379. SMTP
    380. SOAP
    381. SPA (Single-page application)
    382. SQL
    383. SQL Injection
    384. SRI
    385. STUN
    386. SVG
    387. SVN
    388. Safe
    389. Same-origin policy
    390. Scope
    391. Screen reader
    392. Script-supporting element
    393. Scroll container
    394. Scrollport
    395. Search engine
    396. Second-level Domain
    397. Secure Sockets Layer (SSL)
    398. Selector (CSS)
    399. Self-Executing Anonymous Function
    400. Semantics
    401. Serialization
    402. Server
    403. Server Timing
    404. Session Hijacking
    405. Shadow tree
    406. Shim
    407. Signature
    408. Simple header
    409. Simple response header
    410. Site
    411. Site map
    412. Sloppy mode
    413. Slug
    414. Smoke Test
    415. Snap positions
    416. Specification
    417. Speculative parsing
    418. Speed index
    419. Stacking context
    420. State machine
    421. Statement
    422. Static method
    423. Static typing
    424. Strict mode
    425. String
    426. Style origin
    427. Stylesheet
    428. Symbol
    429. Symmetric-key cryptography
    430. Synchronous
    431. Syntax
    432. Syntax error
    433. Synthetic monitoring
    434. TCP
    435. TCP handshake
    436. TCP slow start
    437. TLD
    438. TOFU
    439. TTL
    440. TURN
    441. Tag
    442. Telnet
    443. Texel
    444. Thread
    445. Three js
    446. Time to first byte
    447. Time to interactive
    448. Transmission Control Protocol (TCP)
    449. Transport Layer Security (TLS)
    450. Tratando Formulários com PHP
    451. Tree shaking
    452. Trident
    453. Truthy
    454. Type
    455. Type coercion
    456. Type conversion
    457. UDP (User Datagram Protocol)
    458. UI
    459. URI
    460. URL
    461. URN
    462. UTF-8
    463. UX
    464. Unicode
    465. Usenet
    466. User agent
    467. Validator
    468. Value
    469. Variable
    470. Vendor Prefix
    471. Viewport
    472. Visual Viewport
    473. VoIP
    474. W3C
    475. WAI
    476. WCAG
    477. WHATWG
    478. Web performance
    479. Web server
    480. Web standards
    481. WebDAV
    482. WebExtensions
    483. WebGL
    484. WebIDL
    485. WebKit
    486. WebM
    487. WebP
    488. WebRTC
    489. WebSockets
    490. WebVTT
    491. Whitespace
    492. World Wide Web
    493. Wrapper
    494. XForms
    495. XHR (XMLHttpRequest)
    496. XHTML
    497. XInclude
    498. XLink
    499. XML
    500. XPath
    501. XQuery
    502. XSLT
    503. beacon
    504. buffer
    505. caret
    506. document environment
    507. firewall
    508. frame rate (FPS)
    509. jQuery
    510. lossy compression
    511. markup
    512. mime
    513. minification
    514. non-normative
    515. privileged code
    516. undefined