Final answer:
The word 'because' is a transition word that signifies a cause-and-effect relationship, connecting a cause to its subsequent effect in a sentence.
Step-by-step explanation:
The transition word because indicates a cause-and-effect relationship. It is used to connect two parts of a sentence wherein the first part typically reflects the cause, and the second part shows the effect resulting from that cause. For example, in the sentence 'The game was postponed because it was raining,' the reason or cause for the game's postponement is the rain, and the effect is the game being postponed.
Transitional words are important as they help to create flow in writing, guiding the reader through the text by showing how ideas are connected. Because is specifically used to indicate why something happens (the cause) and what happens as a result (the effect).