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In biochemistry, a symbol used as a prefix to indicate the spatial configuration of certain organic compounds with asymmetric carbon atoms. It is used if an organic compound has a configuration about an asymmetric carbon atom analogous to that of D-glyceraldehyde (the arbitrarily chosen standard), in which the hydroxy (OH) functional group is on the right side of the asymmetric carbon atom in a Fischer projection formula.


The symbol for dextrorotatory.
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

D, d


n., pl. Ds D's, ds d's.
1. the fourth letter of the English alphabet, a consonant.
2. any spoken sound represented by this letter.
3. something shaped like a D.
4. a written or printed representation of the letter D or d.


Biochem. Symbol.
(of a molecule) having a configuration resembling the dextrorotatory isomer of glyceraldehyde: printed as a small capital, roman character (disting. from l-).


dextrorotatory; dextro- (disting. from l-).


Pron. Spelling.
do (esp. before you): How d'you like them?


1. contraction of had: They'd already left.
2. contraction of would: I'd like to see it.
3. contraction of did: Where'd you go?
4. contraction of - ed: She OK'd the plan.


1. deep.
2. depth.
3. diopter.
4. divorced.
5. Dutch.


1. the fourth in order or in a series.
2. (sometimes l.c.) (in some grading systems) a grade or mark indicating poor or barely acceptable quality.
a. the second note of the ascending C major scale.
b. a tonality having D as the tonic.
4. (sometimes l.c.) the Roman numeral for 500. Compare Roman numerals.
5. deuterium.


1. day.
2. December.
3. Democrat.
4. Democratic.
5. Physics. density.
6. Deus.
7. Deuteronomy.
8. Doctor.
9. dose.
10. Dutch.


1. date.
2. daughter.
3. day.
4. deceased.
5. deep.
6. degree.
7. delete.
8. Brit. pence.
[< Latin denāriī]
9. Chiefly Brit. penny.
[< Latin denārius]
10. Physics. density.
11. depth.
12. deputy.
13. dialect.
14. diameter.
15. died.
16. dime.
17. dividend.
18. dollar.
19. dose.
20. drachma.
Random House Kernerman Webster's College Dictionary, © 2010 K Dictionaries Ltd. Copyright 2005, 1997, 1991 by Random House, Inc. All rights reserved.