In their dreams people can obtain symbolic wish fulfillment of the id's desires. The superego hides the real meaning of dreams via symbols. Dreams can be analyzed and their true meaning uncovered. Operational Definitions Theoretical or conceptual definitions are useful because of their generality. Operational definitions are useful because of their precision.
Replication is the hallmark of science.
In order to allow replication one needs precision. Vagueness or ambiguity are not accepted. High degree of precision required in science, compared to everyday life. This allows replication by other scientists. Especially important when dealing with abstract concepts or ones that are not directly observable.