ketoses

https://doi.org/10.1351/goldbook.K03387
Ketonic parent sugars (polyhydroxyketones H–[CHOH]n–C(=O)[CHOH]m–H with three or more carbon atoms) and their intramolecular hemiacetals. The oxo group is usually at C-2. E.g. d-fructose:
K03387.png
Sources:
PAC, 1995, 67, 1307. 'Glossary of class names of organic compounds and reactivity intermediates based on structure (IUPAC Recommendations 1995)' on page 1346 (https://doi.org/10.1351/pac199567081307)
White Book, 2nd ed., p. 129 (https://www.qmul.ac.uk/sbcs/iupac/bibliog/white.html)