The word "living" is commonly used throughout elementary science lessons that focus on the biological world. It is a word teachers often take for granted when teaching life science concepts. How similar the constructed meaning of a common word like "living" is to the meaning intended by the teacher or instructional materials depends on how a student makes meaning out of the language teachers use so freely throughout their instruction. Formative assessment probes can be used to reveal the differing ways elementary students think about common words that make up the language of the science classroom. This article describes the "Is It Living?" probe that can be used to uncover the hidden meanings children construct for the word "living." The probe reveals the various attributes students use to decide whether something is living, and how students interpret those attributes. This probe is best used in a discussion context and is an effective instructional tool used to promote "science talk" and develop the norms of argumentation. (Contains 1 figure.)