What word describes something that is firmly established and habitual?

The word that describes something that is firmly established and habitual is "inveterate." This term is often used to refer to habits, practices, or attitudes that are deeply ingrained and unlikely to change. For instance, someone may be described as an inveterate smoker, which indicates that their smoking is a persistent and longstanding habit.

The roots of "inveterate" come from the Latin "inveteratus," meaning "to grow old." It suggests a sense of permanence and continuity, emphasizing that the characteristic in question has been present for a long time and is resistant to change. This is particularly useful in contexts where a person's behavior or beliefs are difficult to alter because they have become so established over time.

In contrast, the other words do not convey the same sense of habitual tendency or deep-rootedness. "Involute" generally refers to something that is complex or intertwined; "meretricious" describes something that is superficial, flashy, or deceitful in appearance; and "mettle" refers to a person's ability to cope well with difficulties, showcasing resilience or spirit, but does not imply anything about habitual behavior. Thus, "inveterate" is the most fitting choice for describing something that is both firmly established and