Terminology plays a crucial role in developing students’ core competencies in subject knowledge. The ways in which terms are explained in textbooks influence students’ understanding of concepts. This study explored the types of terminology explanations found in high school Earth Sciences textbooks and analyzed their distribution across different editions. Using content analysis complemented by corpus analysis techniques, the study examined term explanation methods across six textbook editions based on a typological framework. The findings indicate that the most commonly used explanation types are descriptions and results. Differences among textbook editions were observed in the selection of explanation types. Different types of scientific explanations tend to involve specific sentence patterns and conjunctions. These explanation types not only function as forms of conceptual narration but also provide references for textbook compilation, instructional practices, and terminology review. Given these findings, the study recommends that teachers focus on improving the identification and comprehension of term explanations during instruction to enhance learning outcomes.