Which word describes someone who often exhibits peculiar habits or traits?

The term that describes someone who often exhibits peculiar habits or traits is "idiosyncratic." This word refers to characteristics or behaviors that are unique to an individual, often highlighting quirks or eccentricities that set them apart from the norm. When an individual demonstrates idiosyncratic behaviors, these traits are typically consistent and distinctive, signifying their personal style or approach to life.

In contrast, the other choices do not convey this notion of personal peculiarities. For instance, "incessant" refers to something that is continuous or unceasing, but does not imply uniqueness in habits. "Indifferent" describes a lack of interest or concern, which is unrelated to the idea of exhibiting peculiar traits, and "isolated" refers to being set apart or separated, which also does not capture the essence of having unusual habits or characteristics. Therefore, "idiosyncratic" is the most fitting choice for describing someone with distinctive and peculiar traits.