In articulatory assimilation one segment becomes articulatorily more similar to a nearby segment, for example, a nasal may become labial before a labial consonant. This can be understood straightforwardly as the extension of an articulation, e.g. labial closure, from the conditioning segment into the target. This process is represented autosegmentally as spreading of an articulatory feature from the conditioning segment onto the target. Many of the patterns discussed in this chapter have treated as assimilatory (e.g. Clements 1991), but they cannot be analyzed as simple feature spreading given a strictly articulatory feature set. For example, coronals can condition vowel fronting, but coronals and front vowels do not share any feature that could account for this process in feature theories like those of Sagey (1986) or Chomsky and Halle (1968). These patterns are listed in (1-2).