(κ) optional final consonant In many languages of the Mainland Southeast Asia linguistic area, such as Chinese, the syllable structure is expanded to include an additional, optional segment known as a medial, which is located between the onset (often termed the initial in this context) and the rime. The medial is normally a semivowel, but reconstructions of Old Chinese generally include liquid medials ( in modern reconstructions, in older versions), and many reconstructions of Middle Chinese include a medial contrast between and , where the functions phonologically as a glide rather than as part of the nucleus. In addition, many reconstructions of both Old and Middle Chinese include complex medials such as , , and . The medial groups phonologically with the rime rather than the onset, and the combination of medial and rime is collectively known as the final. Some linguists, especially when discussing the modern Chinese varieties, use the terms "final" and "rime/rhyme" interchangeably. In historical Chinese phonology, however, the distinction between "final" (including the medial) and "rime" (not including the medial) is important in understanding the rime dictionaries and rime tables that form the primary sources for Middle Chinese, and as a result most authors distinguish the two according to the above definition. Grouping of components In some theories of phonology, syllable structures are displayed as tree diagrams (similar to the trees found in some types of syntax). Not all phonologists agree that syllables have internal structure; in fact, some phonologists doubt the existence of the syllable as a theoretical entity. There are many arguments for a hierarchical relationship, rather than a linear one, between the syllable constituents. One hierarchical model groups the syllable nucleus and coda into an intermediate level, the rime. The hierarchical model accounts for the role that the nucleus+coda constituent plays in verse (i.e., rhyming words such as cat and bat are formed by matching both the nucleus and coda, or the entire rime), and for the distinction between heavy and light syllables, which plays a role in phonological processes such as, for example, sound change in Old English and . Body In some traditional descriptions of certain languages such as Cree and Ojibwe, the syllable is considered left-branching, i.e. onset and nucleus group below a higher-level unit, called a "body" or "core". This contrasts with the coda. Rime The rime or rhyme of a syllable consists of a nucleus and an optional