Duality of patterning is a characteristic of human language whereby speech can be analyzed on two levels:
(1) as made up of meaningless elements (i.e., a limited inventory of sounds or phonemes), and
(2) as made up of meaningful elements (i.e., a virtually limitless inventory of words or morphemes).
Also called double articulation.
"[D]uality of patterning," says David Ludden, "is what gives language such expressive power. Spoken languages are composed of a limited set of meaningless speech sounds that are combined according to rules to form meaningful words" (The Psychology of Language: An Integrated Approach, 2016).