What does pseudorandom mean?
Pseudorandom describes something that appears random but is actually generated by a deterministic rule or algorithm. A pseudorandom number or sequence can resemble genuinely random output closely enough to be useful in simulations, sampling, cryptography, testing, and other applications, yet it remains reproducible and may contain detectable statistical patterns. The term is especially important in computing, where algorithms can generate large sets of values more efficiently than physical random processes while allowing researchers or developers to repeat an experiment under the same conditions. Pseudorandomness should not be confused with actual randomness: its underlying mechanism is systematic, even when its visible results seem unpredictable. The prefix “pseudo-” signals this distinction by indicating that the appearance of randomness is simulated rather than absolute. Understanding the term helps explain why apparently unpredictable software outputs can sometimes be reproduced, analyzed, or reverse-engineered when the generating procedure and any concealed seed are known.
adjectiveAppearing random while actually being generated by a deterministic rule or algorithm. Pseudorandom sequences or numbers possess statistical patterns that are deliberately difficult to predict from their outputs alone.
- Resembling randomness while being produced by a deterministic process, especially by an algorithm or fixed mathematical rule.
"Each run produced a pseudorandom sequence that was difficult to predict without knowing the algorithm."
"Each run produced a pseudorandom sequence that was difficult to predict without knowing the algorithm."
"The simulation used pseudorandom sampling to approximate a much larger experiment."
In computing, pseudorandom is random-looking, not random: a deterministic algorithm creates the illusion of chance.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of pseudorandom
The prefix “pseudo-” comes through New Latin from Greek pseudēs, meaning “false” or “pretended.” “Random” entered Middle English from Anglo-Norman French randon, although the ultimate origin of that word remains uncertain. The compound “pseudorandom” became established in twentieth-century mathematics and computing for deterministic processes designed to produce outputs that resemble random ones.
Related word forms
How pseudorandom is actually used
The term is most common in mathematics, computing, cryptography, statistics, and related technical writing. Both “pseudorandom” and “pseudo-random” are used, although the closed form is now especially common.
Easily confused with pseudorandom
A truly random result has no deterministic generating rule, whereas a pseudorandom result looks random but is produced by an algorithm.