We think of these components as being in some ways finite and in other ways non-finite. And the building blocks of one component form the units of the ones higher than it.

1. The sound-system is capable of infinite minute differences in sound, but no language uses all, or even a large part of the possible differences. Sound systems divide things up into finite units (called "phonemes" or classes of sounds) and therefore the number of sound units is finite i.e. English has a finite number of vowels and consonants; the number of vowels is around 11 or 12, varying by dialect.

2. A set of vocabulary items (the "lexicon"). The set of meaningful units is finite, or sort of: there are often 'old' (archaic, obsolete) words floating around in the language, especially in print. Some may be used by older speakers; some may be recognized for their meaning in context, but wouldn't be 'known' in isolation. So old meanings are going out, and new words are constantly being invented.

   The set of meaningful units in the lexicon is therefore more or less finite, but not exactly the same for every speaker. Some meaningful units have only grammatical meaning, e.g. suffixes on words such as -ing, -s, -ed, -th (as in width etc.) and so on. So we distinguish between

   • lexical meaning and
   • grammatical meaningful units.

   The grammatical morphemes are more finite in number than the former. One example of a fairly new grammatical marker is the suffix 'guys' as in 'you-guys' which marks plurality for a lot of people. Other dialects have 'y'all' for this. The fact that it is becoming a grammatical marker is shown by the way some people make it possessive, i.e. 'you-guys's' [yugayzIz], or in southern dialects 'yallz':

   • 'You guys needs to give me you-guys's receipts so you can get reimbursements.
   • Y'all need to give me y'all's receipts so you can get reimbursements.

3. A grammatical system ("morphology") which puts meaningful elements together into 'words'. The grammar is finite, at any given moment.

4. A syntax, or set of rules to state what the order of elements is in larger utterances, such as 'sentences.' But the output of the syntax, i.e. the sentences people know and recognize, is infinite.

5. A semantic component, where meanings are interpreted. Number of possible meanings is probably also infinite.

Put these together in a kind of hierarchical structure, using the sound system as the first building blocks and working upward from there, gives us the following structure:

We see this kind of structure, built from the ground up, as possessed solely by humans, and not observed for other animals, even primates such as chimps, gorillas, etc. The structure of their communication system is much simpler: fewer 'vocabulary' items, simple syntax, very little innovation.