A relation connects the assigned and intended senses—for instance, bravery shared by a lion and a courageous person. A qarīnah signals that the animal itself is not intended, as in “The lion delivered a speech.”
A semantic relation may exist without a sufficiently clear contextual cue. Accordingly, not every vivid statement can be labeled a metaphor without analysis.
Calling a human being a lion relies on similarity; using “eye” for a watchman relies on a part or functional connection. The kind of relation determines the classification.