What term describes something that accompanies another in a subordinate manner?

The term that describes something that accompanies another in a subordinate manner is "concomitant." This word is used to indicate that one thing occurs alongside another and is often dependent on or related to it, reflecting a subordinate or auxiliary relationship. For example, in discussions of medical conditions, a "concomitant" symptom is one that appears alongside a primary condition, providing insight into the nature of the primary issue.

In contrast, the other options represent different concepts. "Connoisseur" refers to a person who has expert knowledge and refined taste in a particular area, typically related to fine arts or cuisine, and does not imply any subordinate relationship. "Commitment" denotes a pledge or dedication to a cause or engagement, which is unrelated to the concept of accompaniment. "Diagrammatic" refers to something that is represented in a diagram format, which entails visualization rather than the relational aspect specified in the question. Understanding the distinction among these terms highlights why "concomitant" is the most fitting answer.