Rigor means thoroughness, precision, and strict attention to detail. When a scientist conducts an experiment with rigor, she carefully controls every variable, double-checks her measurements, and documents everything precisely. When a detective investigates with rigor, he follows every lead, examines all the evidence thoroughly, and doesn't jump to conclusions.

The word suggests being demanding and exacting in your approach, with high standards for quality and accuracy. A teacher might assign rigorous homework that requires deep thinking and careful analysis. A rigorous training program for athletes systematically builds their skills and endurance through carefully designed exercises that challenge them in specific ways.

You'll often hear about academic rigor, which means serious intellectual challenge and high standards. A rigorous math class requires you to show your work, explain your reasoning, and truly master the concepts, with no room for fuzzy thinking.

The related word rigorous describes something that demands this kind of thoroughness. A rigorous schedule is demanding and disciplined. Rigorous standards are strict and uncompromising. When you approach a project with rigor, you're committing to doing it right, with full attention to quality and detail.