It goes without saying that a sentence need not necessarily be cither only compound or only complex. It may combine both types of clause connections within its structure. Thus, for instance, there may be a compound sentence in which each of the main clauses has one or more subordinate clauses (possibly of different degrees) attached to it. Besides, the subordinate clauses may of course differ from one another in various ways; for example, one subordinate clause may be attributive while another is adverbial, and so forth. Only a detailed investigation of all these varieties as they actually occur in texts will give an adequate idea of the structure of the composite sentence in Modern English. Here we will content ourselves with illustrating the point by the following composite sentence containing both co-ordination and subordination: This was a section that knew the chill of winter, as well as the heat of summer, and there was a vigor and energy in the people that was strange to her. (M. MITCHELL)
Of course, various groupings are possible here: the sentence may bo basically compound, with each of the co-ordinated clauses having one or more subordinate clauses (eventually of different degrees) attached to it, or it may be essentially complex, that is, consisting of a main clause and several subordinate clauses, some of which may be homogeneous and co-ordinated with one another, so that co-ordination appears here, as it were, on a lower level than subordination. The number of types is probably very great. However, much remains to be done in this sphere before the actual picture of composite sentences in Modern English is cleared up.
