ald-
combining form 
or aldo-
Etymology: probably from French ald-, from aldéhyde, from German aldehyd — more at aldehyde 
1. : containing the aldehyde group  — in names of classes of compounds
< aldohexose >
— compare aldehydo-
2. : related to an aldehyde 
< aldimine >
or aldo-
1.
< aldohexose >
— compare aldehydo-
2.
< aldimine >