Primer (molecular biology), a nucleic acid strand (or related molecule) that serves as a starting point for DNA replication
Percussion cap, in ballistics, a small charge that explodes when struck with force or heated with electricity, typically to ignite a larger charge of propellant
Primer (paint), a coating applied to a surface to prepare it for paint or another coating or adhesive
Primer (textbook), a textbook formerly used in primary education (often pronounced "primmer" in General American) to teach the alphabet and other basic concepts
New England Primer, contained moral-themed rhymes associated with the colonial American Puritan culture