What prefix would be used to denote a concept that is "not" something?

The prefix used to denote a concept that is "not" something is "in-". This prefix is commonly employed in medical terminology and other fields to indicate negation or absence. For example, terms like "incomplete" or "invisible" utilize this prefix to convey that something is lacking or not present.

In medical contexts, "in-" can be found in terms such as "inhospitable," meaning not hospitable, or "insufficient," indicating the absence of sufficiency. This usage highlights the versatile nature of the prefix across various disciplines, emphasizing that it serves to modify the root word to express a negated condition or quality effectively.

The other prefixes do not carry the same negation meaning; "my-" typically relates to muscles, "inter-" refers to between or among, and "intra-" denotes within or inside. Thus, "in-" is the appropriate choice for indicating something that is not present or lacking.