The State-Trait Anxiety Inventory (STAI) is a psychological assessment tool designed to measure two types of anxiety: state anxiety, which reflects temporary feelings of anxiety in response to specific situations, and trait anxiety, which indicates a person's general tendency to experience anxiety across various contexts. Developed by Charles D. Spielberger in the 1970s, the STAI consists of two separate self-report questionnaires. Each questionnaire contains a series of statements that respondents rate based on their feelings. The results help psychologists and researchers understand an individual's anxiety levels, guiding treatment and intervention strategies. The STAI is widely used in clinical and research settings to assess anxiety in various populations.