Which word refers to something markedly different from an accepted norm?

The word that refers to something markedly different from an accepted norm is "aberrant." This term is often used to describe behaviors, phenomena, or situations that deviate from the expected or typical standards. When something is characterized as aberrant, it implies that it is unusual or atypical when compared to what is commonly recognized or accepted within a given context.

In contrast, the other terms relate more closely to established norms or standards. "Normative" refers to something that establishes, relates to, or derives from a standard or norm, suggesting conformity rather than deviation. "Commonplace" describes something that is ordinary or unremarkable, indicating widespread acceptance rather than deviation. "Conventional" pertains to what is established and generally accepted; it embodies adherence to traditional norms or practices. Therefore, "aberrant" stands out as the term that specifically captures the idea of significant deviation from what is typically expected.