What is "tetrose"

Tetrose \Tet"rose\, n. [Tetra- + -ose.] (Chem.) A monosaccharide derived from a certain alcohol.

n. (context carbohydrate English) A sugar or saccharide containing four carbon atoms.

n. any monosaccharide sugar containing four atoms of carbon per molecule

A tetrose is a monosaccharide with 4 carbon atoms. They have either an aldehyde functional group in position 1 (aldotetroses) or a ketone functional group in position 2 (ketotetroses).

Fischer.svg | D-Erythrose Fischer.svg | D-Threose Fischer.svg | D-Erythrulose

The aldotetroses have two chiral centers ("asymmetric carbon atoms") and so 4 different stereoisomers are possible. There are two naturally occurring stereoisomers, the enantiomers of erythrose and threose having the D configuration but not the L enantiomers. The ketotetroses have one chiral center and, therefore, two possible stereoisomers: erythrulose (L- and D-form). Again, only the D enantiomer is naturally occurring.