variable) knowledge. Theoretical approaches represented in the collection for accommodating these types of knowledge include modularity, dynamical grammars, and probabilistic grammars. A second major focus is on the acquisition of this knowledge. Here the papers pursue the consequences for acquisition of taking into account the richness and variability of the adult systems that provide input to the child. The final focus is on how phonological knowledge guides speech production. Data and models address the question of how speech gestures interact with one another locally (through articulatory constraints and syllable-level organization) and how they interact with the prosodic structure of an utterance. The twenty-six papers in the collection include invited contributions from Diane Brentari, David Corina, David Perlmutter, D. Robert Ladd, Diamandis Gafos, Marilyn Vihman, Shelley Velleman, Stefanie Shattuck-Hufnagel, and Dani Byrd.