*Benzylidene acetal and acetonide, protecting groups
*Dimethoxymethane, a solvent, a.k.a. methylal, a.k.a. formal [ambiguous]
*Dioxolane
*Metaldehyde
*Paraldehyde
*1,3,5-Trioxane
*Phenylsulfonylethylidene (PSE) acetal is an example of arylsulfonyl acetal possessing atypical properties, like resistance to acid hydrolysis which leads to selective introduction and removal of the protective group.
*Most glycosidic bonds in carbohydrates and other polysaccharides are acetal linkages.
**Cellulose is a ubiquitous example of a polyacetal.
Although many compounds contain an acetal functional group, at least two acetal compounds are called "acetal" for short:
*Polyoxymethylene (POM) plastic, also known as "acetal" or "polyacetal", is a polyacetal (and a polyether), and a polymer of formaldehyde.
*1,1-Diethoxyethane (acetaldehyde diethyl acetal), sometimes called simply "acetal", is an important flavouring compound in distilled beverages.