Nonlinear phonology encompasses a number of theoretical perspectives on the organization of phonological (i.e., speech) systems. Phonological theories prior to the mid-1970s focused on speech sounds or segments (i.e., consonants and vowels) as they occur in contiguous linear sequences made up of a single line of discrete nonoverlapping elements. However, it became clear that some phonological features (e.g., high or low tone or place of articulation) last for longer or shorter periods than a single segment and that segments are grouped into higher units such as syllables; both of these properties cause problems for linear theories. Nonlinear phonological theories in contrast posit multiple lines of elements that last for different periods of time that are shorter (e.g., the feature [Labial]) or longer (e.g., syllables and ...