Optimality Theory (OT) has been a major force
driving developments in formal linguistics during the past decade.
Like parameter-setting accounts, OT seeks to describe the range
within which languages can vary; but instead of fixing parameters,
OT proposes that languages, and children learning languages,
arrange a set of constraints in a hierarchical order of strength
that determines specific linguistic characteristics. The
constraints proposed by OT are constraints on the well-formedness
of the output of a grammar, and they are of two types: (i)
markedness constraints, which exert pressure toward
unmarked types of structure such as CV syllables or voiceless
final obstruents; and (ii) faithfulness constraints,
which maintain lexical contrasts such as CV and CVC syllable
types, or voicing distinctions in final obstruents. The two
types of constraints are in conflict, so that no particular
constraint can be satisfied without violating others. In OT,
“satisfaction” and “violation” are not
absolute but a matter of degree, because all constraints play
a role in the grammar of each language, though in a different
order of strength or priority within a dominance hierarchy.