These words mean equal to what is required or expected, but not exceeding it by much. Adequate means suitable to the case or occasion: an adequate supply of food for the hike. Like satisfactory , adequate may apply to quality as well as quantity: an adequate performance, but nothing to rave about; His knowledge of French was adequate for the job, although he was not fluent in the language. Satisfactory implies a standard to which something is being compared or against which it is being tested.

• The child’s reading ability was satisfactory for his age level; The response to our call for financial contributions was wholly satisfactory , exceeding our goal by several thousand dollars.

Enough is in some contexts interchangeable with adequate, but is used only to indicate amount or degree, not quality. Moreover, unlike adequate , enough is not used after an article and before a noun in this sense. One can say an adequate fuel but not an enough fuel . (Note that adequate fuel can mean either enough fuel or fuel of acceptably high quality , whereas an adequate fuel can refer only to quality.) Enough modifies either plural nouns or nouns denoting something that is measurable or of which there can be a quantity: enough salesmen; enough time; enough air ?but not : enough supply; enough house.

Sufficient implies a quantity or number adequate for a particular need or to fulfil a particular purpose: Our military response to the aggressive act was limited but sufficient to show our determination. Unlike satisfactory , it does not imply measuring up to a standard. It emphasizes instead the end being sought; the degree to which something contributes to the achievement of that end is what makes it sufficient or insufficient .