This study was carried out to analyze terms in primary science textbooks. The results of the research are as follows. 1. The higher-grade science textbooks use more types of categories and less definitions for terms. Only 14% of definitions for terms are showed in textbooks, and no more than 0.4~0.6 definitions shows the shortage of definitions for terms in one class content. 2. The definitions by contract, which forms 68%, was the highest in elementary science textbooks. And the dictionary definitions, which are 62%, was the highest in experiment-observation textbooks. 3. The most used type of definitions is the way which is used for a case or a indicating methods, and its rate is increasing steadily. And its rate was 76% of the whole of terms. 4. Terms used in energy field are few as compared with terms of other fields. Each field has completely different ways of defining terms and presenting content in textbooks to other fields.