[with] + [very] -- the building blocks of poetry
Poetic meter is created from two fundamental linguistic structures — syllables and stress.
Spoken speech is a continuous stream of sound. Syllables are the way that we mentally group different sounds with one another and break this continuous stream into discrete units. Mathematically, we are trying to determine where to place parentheses. For example, if we are given a speech stream [a b c d e f g h i j k], which way of bracketing is correct?
[a b] [c d e] [f g] [h i] [j] [k]
[a b c] [d e f g h] [i j] [k]
[a] [b] [c d e f] [g h] [i j k]
etc.
This is a highly nontrivial question. In fact, this “segmentation” process is so critical to understanding the grammar of the mother language that infants begin doing it very early on, perhaps even in utero.
Stress is a concept that eludes precise definition. We can think of it as an increase in pitch, volume, or syllable length. Essentially, it is a way to “mark” a syllable as different from a regular, unstressed syllable.
Languages like Latin and Greek are conceived of in terms of long and short, rather than stressed and unstressed, syllables. In their metrical theories, a long syllable is sounded for twice as long as a short syllable. This suggests that the correct way to think about stress is as a reduplication. Schematically, the two types of syllables can be represented as follows.
unstressed / short = a
stressed / long = <a a>
The various meters that we encounter in poems are simply arrangements of syllables and stresses into patterns. Precisely what these patterns are is unimportant from a cognitive point of view.