As we already know the Grammar of Language embraces all its levels and units. The problem here is: How many and what sorts of units must we recognise to be sure that our model of Language (=theory of Language) should be a correct representation of it?
Solution of the problem depends on how we answer another question: What is Language? We shall not now discuss it because this question was discussed at length in other courses. We shall simply use the results. And the result is that Language is a means of communication. If so, the structure of Language, the number and properties of its components, units are determined by its function. It means that they depend upon the aim the means is used for and the manner it can be used. The main aim of Language due to its definition is to create conditions for communication. So the biggest structure Language should provide us with is a dialogue. Then it must give us a possibility to show our position in the event we speak about. So the next structure is a communicative part. Then we have to inform each other about the matter we speak, about our aims and about what we want our partners to do. So the next structure is an UTTERANCE or in, other terms, text. Then we have to correlate our informative structures with "the actual life as we know it", producing sign models of necessary fragments if that life, and Language provides us with a sentence. Sentences being models of fragments of states of things must represent relations of things for which end Language provides us with members of sentence. Because relations can exist only if there are objects we need names of these objects and Language provides us with words. Then words to operate as names need elements which we know as morphemes. And finally we find phonemes.
The units and their functions which we have just listed constitute levels of Language. You know from the course of “Introduction into Linguistics” that such units as phoneme and morpheme exist only as variants. One cannot pronounce a phoneme or a morpheme. We pronounce (allo)phones or (allo)morphs. The same is true for other units mentioned in the paragraph above. We cannot pronounce a whole word. We pronounce a form of a word. The units we actually pronounce or hear or see or write are known as concrete or etic units. The units of the paragraph above< those which cannot pronounce or hear or see or write themselves but only by pronouncing or hearing or seeing or writing their etic representations are known as abstract or emic units.
Since Grammar presupposes unity of form and meaning it can start with morphs and morphemes and spread up to the dialogues if the other units listed above represent some of their meaning through opposites of their variant which in this case should be treated as grammatical forms.