The construction of all models requires the identification and representation of 1) a set of structural elements and 2) a syntax. The structural elements are the "building blocks" of a model. The syntax is the set of rules or directives that describe how the building blocks may be put together.

In linguistic models, for example, the structural elements are typically words: written and/or spoken vocabularies. The syntax is the set of grammatical rules that dictate how the various words may be fitted together. The English language has a relatively small vocabulary (about 36,000 words), yet throughout the history of English speaking people, millions of different sentences have been uttered and millions of different ideas have been put into words. This is possible because the words may be assembled in different orders, sequences and forms which provide particular contexts in which words can evoke unique meaning and significance. All the books ever written in the English language are composed of the same words used over and over in different orders; the words, in turn, are assembled from the same twenty–six letters of the alphabet.

To be a fluent speaker of the language, one does not have to memorize all possible word combinations accepted as being well–formed sentences. That would be impossible. Yet somehow, we know that certain sequences of words constitute understandable sentences while others do not. For example, consider the previous sentence with the words reversed: