Marked, unmarked, and derived structure
By definitions, derivations start at some notional ‘bottom’, and are necessarily ordered. To the greatest degree possible, this ordering should follow from conceptual necessity. This ordering is partly given by the notion of markedness. The least marked elements in a structure are implemented last in the order of derivation.
There are degrees of markedness. Take the sound structure of a word like strange, with a cluster of three phonemes in the onset and a cluster with N and the affricate represented by GE. Such a word represents a high degree of markedness in its sound structure. Conversely, the CV structures of Mummy and Daddy or Mama and Dada and so on, are minimally marked.
Similar or identical consonants occur in the overwhelming majority of languages.
To a degree, there is a natural sequence in children’s acquisition of speech and language from, the least marked to the most marked. But only to a degree.
Markedness is a measure of how much information has to be added to a structure in the course of its derivation. Unmarked structure represents what can be implemented by default.