Metrical tree

In phonology, a metrical tree is a branching representation of stress, introduced by Liberman & Prince (1977) in the framework of metrical phonology. A metrical tree is a hierarchy in which syllables are combined into feet and feet into a word constituent. Higher level structure includes the phonological phrase, intonational phrase and utterance (cf. Selkirk (1981), Nespor & Vogel (1986)). Pairs of sister nodes are labeled Weak-Strong or Strong-Weak (or by the Lexical Category Prominence Rule).

Example
The English phrase achromatic lens is represented as follows:

/ \                /   \                /     \               /       \              w         s           /     \      | Fw      Fs    F	              /  \     /  \    \ Ss  Sw   Ss   Sw   S      |     |   |    |    | a  chro  ma  tic lens

where S = syllable, w = weak, F = foot,	   s = strong

Comments
Hayes (1981) constrained metrical theory considerably by the introduction of a universally defined set of parameters that characterize the stress systems of languages (i.e. bounded/unbounded; dominance (left/right), direction of footing, quantity-(in)sensitivity).

Link
Utrecht Lexicon of Linguistics