Several commonly used terms in homopteran feeding behavior and vector literature have been poorly defined, or defined differently by different researchers in their papers. This has led to considerable confusion in the literature, especially for students and researchers entering the field. This chapter seeks to clarify 4 particularly fundamental terms—ingestion, feeding, probing, and stylet penetration,—and to make recommendations for their use in the future. Ingestion is defined as to take up food into the alimentary canal, past the true mouth, and is recommended as the sole term used for uptake of fluid. The term feeding has variously been used by homopterologists worldwide, but is recommended to be defined solely in the broad sense as all activities that are involved in obtaining, handling and ingesting food. Finally, the terms probing and stylet penetration should now be synonymized and de-teleogized, by defining both as the process of stylet insertion into the plant, regardless of its duration or purpose. Grammatical and scientific justifications of these definitions are discussed.