Secondary research is burgeoning in the field of Applied Linguistics, taking the form of both narrative literature review and especially more systematic research synthesis. Clearly purposed and methodologically sound secondary research contributes to the field because it provides useful and reliable summaries in a given domain, facilitates research dialogues between sub-fields, and reduces redundancies in the published literature. It is important to understand that secondary research is an umbrella term which includes numerous types of literature review. In this commentary, we present a typology of 13 types of well-established and emergent types of secondary research in Applied Linguistics. Employing a four-dimensional analytical framework, focus, review process, structure, and representation of text of the 13 types of secondary research are discussed, supported with examples. This article ends with recommendations for conducting secondary research and calls for further inquiry into field-specific methodology of secondary research.