tau

American  

[tou, taw, tahv, tawv] / taʊ, tɔ, tɑv, tɔv /

noun

1. the 19th letter of the Greek alphabet (T,τ ).

2. the consonant sound represented by this letter.

3. tav.

4. Physics. Also tauon tau lepton.

5. Also called tau protein.  Biochemistry. a protein that is an important component of nerve cells, helping to maintain their function and structure: in the brain, distortions in the protein’s molecular shape is associated with the onset of Alzheimer’s disease.

---

tau British  

/ taʊ, tɔː /

noun

1. the 19th letter in the Greek alphabet (Τ, τ), a consonant, transliterated as t

---

Etymology

Origin of tau

1250–1300; Middle English < Latin < Greek taû < Semitic; cf. tav

Example Sentences

Specialized blood tests and brain scans can now identify the toxic forms of amyloid and tau protein in the brain that confirm a diagnosis of Alzheimer’s disease.

From The Wall Street Journal • Jun. 20, 2026

As autophagy slows in older adults, a-beta may accumulate inside neurons and increasingly compete with tau for access to microtubules.

From Science Daily • Jun. 19, 2026

As a result, when a-beta accumulates inside neurons, it can potentially push tau out of its normal position.

From Science Daily • Jun. 19, 2026

Drugmakers are also developing medications that target tau tangles in the brain so patients may have more options in the future.

From The Wall Street Journal • Jun. 15, 2026

However, if T. tau and T. upsilon are subspecies, intergrades would be expected between the ranges of the two populations and not on the northeastern and southwestern periphery of their combined ranges.

From The Amphibians and Reptiles of Michoacán, México by Duellman, William E.