We investigated the physical production of speech sounds in terms of the articulatory mechanisms of the human vocal tract. That investigation was possible because of some rather amazing facts about the nature of language. When we considered the human vocal tract, we didn’t have to specify whether we were talking about a fairly large person, over six feet tall, weighing over 200 pounds, or about a rather small person, about five feet tall, weighing less than 100 pounds. Yet those two physically different individuals would inevitably have physically different vocal tracts, in terms of size and shape. In a sense, every individual has a physically different vocal tract. Consequently, in purely physical terms, every individual will pronounce sounds differently. There are, then, potentially millions of physically different ways of saying the simple word me.

In addition, each individual will not pronounce the word me in a physically identical manner on every occasion. Obvious differences occur when that individual is shouting, is suffering from a bad cold.

Given this vast range of potential differences in the actual physical production of a speech sound, how do we manage consistently to recognize all those versions of me as the form [mi], and not [ni] or [si] or [ma] or [mo] or something else entirely? The answer to that question is provided to a large extent by the study of phonology.