Have you ever built a tree house? If so, what did you use to build it? What kinds of materials? Did you have a plan? Maybe you used

• lumber of different sizes and functions;
• fasteners, such as nails and screws of different sizes; and
• a blueprint or rough idea of what you want the tree house to look like.

Building a tree house takes planning, materials, and know-how. Building a written composition also takes planning, materials, and know-how, although of a different sort. Consider the lumber you use to build the tree house. Each piece must be complete in and of itself. You can’t very well nail up a piece of lumber that is broken and splintered. The lumber must be complete in order to make the structure of the tree house sound. You can think of sentences in the same way. They too must be complete, expressing complete thoughts, in order to form a cohesive composition.

The lumber, though, is not the only material to consider when building a solid tree house. The fasteners, the screws and nails, must be of adequate length and strength to join the pieces of lumber together. Some sentences must have fasteners, too, in the form of conjunctions. The conjunctions work like fasteners in these sentences because they join the clauses, the parts of sentences, together. Conjunctions must be chosen carefully in order to communicate your ideas effectively.

Just as building a tree house can be overwhelming, building a composition can be overwhelming, too. If you have a blueprint and can break the project down, working on it step-by-step, you could end up with a skyscraper. The sky is literally the limit! In this lesson, however, we are not building an entire composition (a persuasive essay, a short story, or a research paper), but rather we are building one element of a composition—interesting and correctly manufactured sentences. Specifically, we are going to learn how to use and understand main clauses and subordinate clauses to achieve this goal.