An ITU-T Recommendation (1988) for a public key infrastructure (PKI). X.509 establishes a hierarchical structure of certificate authorities (CAs) that issue digital certificates, which are electronic credentials that authenticate the identity of users on the Internet and intranets. See also authentication, CA, digital certificate, Internet, intranet, and PKI.
An international standard (1988) developed jointly by the International Organization for Standardization (ISO) and the ITU-T to support the e-mail name and address lookup requirements of X.400. X.500 provides for global directory services that theoretically enable network managers to store information about all users, machines, and applications in a distributed fashion. X.500 is a very robust global directory standard that requires significant computational resources to implement and, therefore, is criticized for being over-engineered. See also e-mail, ISO, ITU-T, LDAP, X.400, and X Series.
The symbol for reactance. See reactance.
- the basic elements of a specified field of work, knowledge, etc.; often, specif., the plays and strategies used in a particular sport
Idioms, Phrasal Verbs Related to X
Origin of X
X is prototypically pronounced [ks] in English; it therefore serves as a convenient shorthand for the digraphs (cs, ks, etc.) or trigraphs (cks etc.) that would otherwise represent that consonant cluster.
The x functions as a wildcard; many similar processors also had names ending in 86.
From the French plural suffix -x.