1. the 19th letter of the Greek alphabet (Τ, τ)
2. a mathematical constant equal to the ratio of a circle’s circumference to its radius, approximately 6.28
Usage: mathematics
3. a type of protein found in nerve cells that helps maintain cell structure
Usage: biology; medicine

Examples

• The Greek letter tau appears frequently in mathematical equations.
• Students learned to write both the uppercase and lowercase forms of tau.
• Some mathematicians prefer using tau instead of pi for certain calculations.
• The tau constant equals two times pi.
• Abnormal tau proteins are associated with Alzheimer’s disease.
• Researchers studied tau accumulation in brain tissue samples.