insufficient

Insufficient is an adjective meaning not enough to meet a need or standard. It denotes a lack of adequacy in quantity, quality, or sufficiency, and is often used in formal or technical writing. The term can describe conditions, evidence, resources, or measurements that fail to fulfill a required threshold.

Etymology: from Latin insufficiens, from in- "not" + sufficiens "sufficient". It entered English in the 15th–16th centuries and is closely related to but more formal than inadequate or deficient.

In law and policy, insufficiency appears in phrases such as insufficient evidence or insufficient funding, indicating that a decision cannot be supported or a program cannot be implemented given the current information or resources. In science and statistics, insufficient data or sample size means the data are inadequate for reliable conclusions. In medicine, insufficiency may refer to an inadequate supply or function, such as hypofunction of an organ or insufficient oxygenation. In computing and engineering, insufficient resources can cause failures or degraded performance.

Common synonyms include inadequate, deficient, and lacking, while opposite terms are sufficient and adequate. Usage tends toward a formal tone; in everyday speech people might say not enough or lacking.

See also: sufficiency, sufficiency principle, inadequate, deficiency.