The IUPAC suffix used for aldehydes is “-al.”
In systematic organic nomenclature, an aldehyde is generally named by changing the ending of the corresponding alkane to “-al.” Thus, methane becomes methanal, ethane becomes ethanal, and propane becomes propanal. The aldehyde carbonyl carbon is included in the parent chain and is automatically assigned position 1.
Aldehydes contain the functional group –CHO: a carbon atom double-bonded to oxygen and single-bonded to hydrogen. The terminal hydrogen is what distinguishes an aldehyde from a ketone, whose carbonyl carbon is bonded to two carbon groups. The suffix “-one” is therefore associated with ketones, not aldehydes.
Some aldehydes are better known by traditional names. Methanal is commonly called formaldehyde, ethanal is acetaldehyde, and benzaldehyde retains a widely used accepted name. When the aldehyde group is attached to a ring or cannot be included in the parent chain, nomenclature may use “-carbaldehyde” or the prefix “formyl-.”
The “-al” ending has priority rules and may not be used when another functional group has higher naming precedence. For ordinary aldehydes, however, “-al” is the canonical answer.