Final answer:
A patient with capacity is 18 or older, or emancipated, and must be mentally competent, informed, voluntary, and capable of making healthcare decisions. Children cannot consent for themselves; parents do so until they reach legal adulthood or emancipation.
Step-by-step explanation:
A patient with capacity will be of legal age, which is typically 18 years or older, or emancipated. In addition, the patient will be mentally competent, informed, voluntary, and capable of making healthcare decisions. This means they are able to understand the relevant information presented to them about their medical treatment, appreciate the potential consequences of their decisions, and communicate a clear choice. Parents can provide consent on behalf of their children because, typically, children are not legally considered competent to provide consent for themselves until they reach adulthood or are legally emancipated.