Final answer:
A sign with no necessary or natural connection to the thing it stands for is called a metaphor, a powerful tool in symbolism that relies on shared cultural understanding to communicate abstract ideas.
Step-by-step explanation:
The term that refers to a sign that has no necessary or natural connection to the thing it stands for is a metaphor. Symbols can convey strong messages when used out of their usual context or in a manner that defies cultural norms, thus altering their meanings or giving rise to new interpretations. For example, wearing pajamas to class, historically associated with privacy and bedtime, challenges traditional expectations and conveys an alternative message. Metaphors and other forms of symbolism, such as manas or metonyms, play significant roles in how we communicate concepts and ideas that cannot be directly shown, often relying on cultural or shared understanding to convey their meaning.