What does asynchronous mean?
Asynchronous is an adjective describing things that do not occur, operate, or progress at the same time or at the same rate. Its most prominent modern use is in computing, where asynchronous operations run independently of a master clock: a program can issue a request and continue working rather than sitting idle until the response arrives, and asynchronous data transmission lets devices exchange information without synchronized timing. The word has also become familiar outside engineering through remote work and online education, where asynchronous learning or collaboration means participants engage on their own schedules — watching recorded lectures or answering messages when convenient — rather than gathering live. It contrasts directly with synchronous, which denotes simultaneous or real-time activity. Formed from Greek roots meaning 'not' and 'time', the term entered English through scientific writing and now sits comfortably in both technical documentation and everyday discussion of how modern work gets done.
adjectiveNot occurring, existing, or operating at the same time or at the same rate; in computing, relating to operations that proceed independently of a central clock or without waiting for other processes to complete.
- Not occurring or existing at the same time or at the same rate; having parts that are out of step with one another in time.
- In computing and telecommunications: relating to processes, data transmission, or operations that proceed independently of a shared clock or timing signal, so that a sender and receiver need not be coordinated in real time.
"The course is asynchronous, so students can watch the lectures whenever it suits their schedule."
"Because the team works across three time zones, nearly all their collaboration is asynchronous, conducted through documents and recorded video rather than meetings."
"The microcontroller handles asynchronous serial communication, transmitting data bits without a shared clock signal between devices."
Every time you send an email instead of making a phone call, you're choosing asynchronous communication — and the word comes straight from Greek 'chronos', meaning time.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of asynchronous
Asynchronous derives from Greek roots: the prefix a- ('not'), the element syn- ('together, with'), and chronos ('time'), giving the literal sense of 'not occurring at the same time'. It was formed on the model of the earlier adjective synchronous, which English had adopted from post-classical Latin and Greek sources around the early 17th century; asynchronous appeared somewhat later as scientists and engineers needed a term for phenomena out of temporal alignment. Its cognates share the Greek root chronos, including words like chronology, synchronize, and anachronism.
Related word forms
How asynchronous is actually used
The word belongs chiefly to technical registers — computer science, telecommunications, engineering — but has broadened into general usage through remote work and online education, where 'asynchronous' describes work or learning done on one's own schedule rather than live. In everyday speech it is often shortened informally to 'async' among programmers. It carries no strong emotional connotation; its tone is neutral-to-technical.
Easily confused with asynchronous
Synchronous means occurring or operating at the same time or in real time together, whereas asynchronous means not happening at the same time or rate.
Diachronic refers to change over historical time (as in linguistics), while asynchronous simply describes events or processes not occurring simultaneously.