SINCE 1828

An Encyclopædia Britannica Company

Medical Dictionary

tachysterol

play play

noun ta·chys·ter·ol \ta-ˈkist-ə-ˌrȯl, -ˌrōl\

Medical Definition of tachysterol

: an oily liquid alcohol C₂₈H₄₃OH isomeric with ergosterol that is formed by ultraviolet irradiation of ergosterol or lumisterol and that on further irradiation yields vitamin D₂—see dihydrotachysterol

Seen and Heard

What made you want to look up tachysterol? Please tell us where you read or heard it (including the quote, if possible).

show

WORD OF THE DAY

nobby

play

cleverly stylish

Words at Play

a-woman-waits-at-the-end-of-a-gloomy-pier-does-she-wait-for-charon-the-ferryman-to-the-underworld-it-is-dark-but-she-carries-a-parasol

Great Words for Twilight and Darkness

Words for the goth in all of us

bunch-of-yellow-balloons-lit-by-the-sun

Helium: This Word Brought to You by a Solar Eclipse

And by the Sun, with some help from Greek.

watercolor-squares

We're Down With You Being—or Your Being?—a Square

It's about (you? your?) having your say.

Devilish Words

Don't blame a word use error on the devil.

Ask the Editors

video-title-words-of-the-year-1066

Words of the Year: 1066

Or, Why Pig Meat is Called 'Pork' and Cow Meat is Called 'Beef'

How Often Is 'Biweekly'?

Don't get us started on 'bimonthly'

video-irregardless-grammar-peeve-blend-of-the-synonyms-irrespective-and-regardless

Irregardless

It is in fact a real word (but that doesn't mean you should use it).

video-moose-goose-weird-plurals

Weird Plurals

One goose, two geese. One moose, two... moose. What's up with that?

Word Games

time-traveler-quiz-which-word-came-first

Time Traveler Quiz: Which Word Came First?

Which word entered the English language first?

Take the quiz

Name More Food!

Test your knowledge of food vocabulary!

Take the quiz

Spell It

Can you spell these 10 commonly misspelled words?

Take the quiz

Word Winder's CrossWinder

Word Winder's CrossWinder

A game of winding words.

Play the game