I didn't know this so I hope this benefits some people:
http://en.wikipedia.org/wiki/IUPAC_nomenclature_of_organic_chemistry#Ketones
If a higher precedence suffix is in use, the prefix "oxo-" is used: CH3CH2CH2COCH2CHO is 3-oxohexanal.
http://en.wikipedia.org/wiki/IUPAC_nomenclature_of_organic_chemistry#Ketones
If a higher precedence suffix is in use, the prefix "oxo-" is used: CH3CH2CH2COCH2CHO is 3-oxohexanal.