Which term describes an individual who cannot legally enter into a contract?

The term that describes an individual who cannot legally enter into a contract is "incompetent." In the context of contract law, incompetence refers to a person's lack of legal capacity to form a binding contract. This can arise from various factors, such as age (minors), mental incapacity, or intoxication. Individuals who are deemed incompetent may be unable to understand the nature and consequences of the agreement they are entering into, which is why the law protects them from being bound by contracts.

In contrast, the other terms do not relate to the ability to enter into contracts. "Increment" generally refers to an increase or addition, often related to quantities or amounts, and does not pertain to contractual competence. "Inchoate" typically describes something that is incomplete or not fully formed, which does not directly speak to an individual's capability to contract. Lastly, "investor" refers to a person or entity that allocates capital with the expectation of financial returns, and while investors can enter into contracts, the term does not imply anything about their legal ability to do so. Thus, "incompetent" is the correct term for someone who cannot legally enter into a contract.