tau

noun

ˈtau̇  ˈtȯ 

1

: the 19th letter of the Greek alphabet see Alphabet Table

2

: a short-lived elementary particle of the lepton family that exists in positive and negative charge states and has a mass about 3500 times greater than an electron

called also tau particle

3

: a protein that binds to and regulates the assembly and stability of neuronal microtubules and that is found in an abnormal form as the major component of neurofibrillary tangles

Examples of tau in a Sentence

Recent Examples on the Web

In addition to longitudinal data spanning decades, the Framingham Heart Study provides access to midlife biological measures, like serum cortisol, as well as rich neuroimaging data, including PET scans for proteins associated with Alzheimer’s disease, like amyloid and tau, Salardini says. —Elizabeth Yuko, Flow Space, 5 June 2025

Right now, doctors rely on brain scans called PET scans to find amyloid plaques or do a spinal tap to check for abnormal levels of proteins like beta-amyloid and tau. —Allen Chang, ABC News, 29 Apr. 2025

Long-running studies begin to bear fruit In the 1980s, researchers studying the autopsied brains of people with Alzheimer’s discovered that they were clogged with sticky plaques made from beta amyloid proteins and toxic tangles made of a protein called tau. —Brenda Goodman, CNN, 19 Mar. 2025

One notable pattern was the location of tau deposits. —Jenny Lehmann, Discover Magazine, 9 June 2025

Word History

Etymology

Middle English taw, from Latin tau, from Greek, of Semitic origin; akin to Hebrew tāw taw

First Known Use

14th century, in the meaning defined at sense 1

Phrases Containing tau

• tau cross

Kids Definition

tau

noun

ˈtau̇ 

ˈtȯ

: the 19th letter of the Greek alphabet

—Τ or τ

Medical Definition

tau

noun

ˈtau̇  ˈtȯ 

: a protein that binds to and regulates the assembly and stability of neuronal microtubules and that is found in an abnormal form as the major component of neurofibrillary tangles

called also tau protein