Design features of language b.duality: --the property of having two levels of structures,units of the primary level (e.g.words with meaning)being composed of elements of the secondary level (e.g. sounds with no meaning)and each level having its own principles of organization. two sets of structures: one of the sounds which is physical,external the other of meaning which is internal and abstract.Design features of language b. duality: --the property of having two levels of structures, units of the primary level (e.g. words with meaning) being composed of elements of the secondary level (e.g. sounds with no meaning) and each level having its own principles of organization. two sets of structures: one of the sounds which is physical, external the other of meaning which is internal and abstract