This is called RANDOMNESS
Randomness :
adjective
1.proceeding, made, or occurring without definite aim, reason,or pattern:
the random selection of numbers.
2.Statistics. of or characterizing a process of selection in whicheach item of a set has an equal probability of being chosen.
3.Building Trades.(of building materials) lacking uniformity of dimensions:
random shingles.
(of ashlar) laid without continuous courses.constructed or applied without regularity:
random bond.
4.Informal.unknown, unidentified, or out of place:
A couple of random guys showed up at the party.
odd and unpredictable in an amusing way: my totally random life.
noun
5.Chiefly British, bank3(def 7b).
adverb
6.Building Trades. without uniformity:
random-sized slates.
Idioms
7.at random, without definite aim, purpose, method, oradherence to a prior arrangement; in a haphazard way:
Contestants were chosen at random from the studioaudience.
