Annisa Dewanti, K2217012. First supervisor: Prof. Dr. Joko Nurkamto, M.Pd. Second supervisor: Dra. Dewi Rochsantiningsih, M.Ed., Ph.D. “VOCABULARY BUILDING IN ENGLISH TEXTBOOK FOR THE ELEVENTH GRADE OF SENIOR HIGH SCHOOL: A CONTENT ANALYSIS”. Thesis, Surakarta: Teacher Training and Education Faculty of Sebelas Maret University, June 2024. The intent of the present study is to ascertain: 1) the types of learning activities for vocabulary building (LA for VB) are available in the senior high school grade 11 textbook "Bahasa Inggris Tingkat Lanjut"; and 2) the element of vocabulary mastery is supported by learning activities for vocabulary building (LA for VB) within the same textbook. As the methodology for this inquiry, a content analysis is used. Additionally, the data are gathered by document analysis, which involves picking and reading each chapter of the primary source a senior high school textbook "Bahasa Inggris Tingkat Lanjut" choosing the learning activity for vocabulary building, and assigning codes to the information. The result of this study reveals that: 1) there are 6 (35%) out of 17 types of learning activities of VB founded in the textbook “Bahasa Inggris Tingkat Lanjut” with include: a) word and meaning matching, b) sentence completion, c) semantic analysis, d) interpreting dictionary entiries, e) sentence making activity and, f) asking and answering. 2) there are 5 (five) vocabulary element that should be mastery by the student, which included: a) pronunciation, b) spelling, c) meaning, d) classification, and e) use in context. The results indicated that each of the six LA for VB identified in this study provided assistance for each vocabulary element in a different way. Furthermore, it is advised that teachers could prepare other LA that reinforce VB beyond the scope of the identified learning activities.Keywords: content analysis, elements of vocabulary mastery, English textbook, learning activity, vocabulary building