This study aims to produce two-dimentional geometri module based on the APOS theory for 4^th grader students is valid and feasible. This research method is research and development (R&D) using a 4D development model (define, design, develop, and disseminate). However, in this study, the 3-D development was modified, namely the disseminate stage was not carried out due to limited time, energy, and cost in carrying out this research. The subject of this research is the 4^th grader of Semarang State Islamic Elementary School (MIN Semarang). Based on the results of the study, it was found that (1) module assessment by material and media expert the quality of the module quality by material and media expert validators is in the very good category with a value of 4,7 and 4,4. (2) Student learning outcomes from field trials obtained an average of 79,8 with a completeness level of 78.6%. It can be concluded that the product of two-dimentional geometri module based on the APOS theory is valid and feasible for use in learning

Daryanto. (2013). Menyusun Modul: Bahan Ajar Untuk Persiapan Guru Dalam Mengajar. Yogyakarta: Gava Media.

Departemen Pendidikan Nasional. (2008). Panduan Pengembangan Bahan ajar. Jakarta: Direktorat Jenderal Manajemen Pendidikan Dasar dan Menengah.

Dubinsky, E., & Mcdonald, M. A. (2001). APOS: A Constructivist Theory of Learning in Undergraduate Mathematics Education Research. 1–22.

Gradini, E., Mulyani, S. R., & Asnawi, A. (2021). Development of Social Arithmetic Teaching Materials with Islamic Characters on 7th Grader Students. Eduma : Mathematics Education Learning and Teaching, 10(1), 27. https://doi.org/10.24235/eduma.v10i1.8062

Herlina, E. (2013). Meningkatkan Disposisi Berpikir Kreatif Matematis Melalui Pendekatan Apos. Infinity Journal, 2(2), 169. https://doi.org/10.22460/infinity.v2i2.33

Inglis, M. (2015). Review of APOS theory: A framework for research and curriculum development in mathematics education, Arnon et al. (2014). International Journal of Research in Undergraduate Mathematics Education, 1, 413–417. Retrieved from http://link.springer.com/10.1007/s40753-015-0015-9

Junaedi, I., & Asikin, M. (2012). Pengembangan Pembelajaran Matematika Humanistik Untuk Meningkatkan Kemahiran Matematis. Unnes Journal of Mathematics Education Research, 1(2), 114–120. Retrieved from https://journal.unnes.ac.id/sju/index.php/ujmer/article/view/647

Lestari, D., Darmawijoyo, & Aisyah, N. (2018). Pengembangan LKS Berbasis Teori APOS Pada Materi Bangun Ruang Sisi Datar di SMP dengan Konteks Rumah Adat Musi Banyuasin. Kreano: Jurnal Matematika Kreatif-Inovatif, 9(1), 1–9. https://doi.org/10.15294/kreano.v9i1.12259

Marsitin, R. (2017). Modul Pembelajaran Limit dengan Teori Apos. Seminar Nasional Hasil Penelitian Universitas Kanjuruhan Malang, 5(1), 444–450. Retireved from https://semnas.unikama.ac.id/lppm/prosiding/2017/4.PENDIDIKAN/24.%20Retno%20Marsitin_Penelitian_Pendidikan.pdf

Maryam, M., Masykur, R., & Andriani, S. (2019). Pengembangan e-modul matematika berbasis Open Ended pada materi sistem persamaan linear dua variabel kelas VIII. AKSIOMA : Jurnal Matematika Dan Pendidikan Matematika, 10(1), 1–12. https://doi.org/10.26877/aks.v10i1.3059

Mulyono, M. (2011). Teori Apos Dan Implementasinya Dalam Pembelajaran. Journal of Mathematics and Mathematics Education, 1(1). https://doi.org/10.20961/jmme.v1i1.9924

Ningsih, Y. L. (2017). Kemampuan Pemahaman Konsep Matematika Mahasiswa Melalui Penerapan Lembar Aktivitas Mahasiswa (LAM) Berbasis Teori APOS Pada Materi Turunan. Edumatica, 6(1), 1–8. Retrieved form https://online-journal.unja.ac.id/edumatica/article/view/2994

Oktari, T, Hartono, Y & Santoso, B. (2017). Pengembangan LKS Berbasis APOS Berbantuan Microsoft Excel Pada Pokok Bahasan Program Linier Di SMK. Jurnal Pendidikan Matematika RAFA, 2(2), 229–248. Retrieved from http://jurnal.radenfatah.ac.id/index.php/jpmrafa/article/view/1250

Prasetyo, K. B. (2020). The APOS Content Basic Algebra Module to Improve the Learning Autonomy of Achieving Mathematics Connection Skills. Unnes Journal of Mathematics Education Research, 10(2), 136–143. Retrieved from https://journal.unnes.ac.id/sju/index.php/ujmer/article/view/45485

Prastowo. (2011). Panduan Kreatif Membuat Bahan Ajar Inovatif. Yogyakarta: Diva Press.

Sukestiyarno, & Rahmawati, Y. (2019). Geometri Ruang Berdasarkan Teori APOS Bermuatan Karakter Kemandirian dan Komunikasi Matematis. Yogyakarta: CV Andi Offset.

Thiagarajan. Semmel & Semmel. (1974). Instruction Development for Training Teachers of Exceptional Childreen A Sourcebook. Indiana: Indiana University Bloomington.

Tjiptiany, E. N., As’ari, A. R., & Muksar, M. (2016). Pengembangan Modul Pembelajaran Matematika Dengan Pendekatan Inkuiri Untuk Membantu Siswa Sma Kelas X Dalam Memahami Materi Peluang. Jurnal Pendidikan: Teori, Penelitian, Dan Pengembangan, 1(10), 1938–1942. Retrieved from http://journal.um.ac.id/index.php/jptpp/article/view/6973

Widoyoko, E. P. (2010). Evaluasi Program Pembelajaran. Yogyakarta: Pustaka Pelajar.

Wijayanti, K., Waluya, S. B., Kartono, & Isnarto. (2018). Kemampuan Mengkonstruksi Bukti pada Materi Grup dalam Pembelajaran Berbasis APOS. Prisma, Prosiding Seminar Nasional Matematika, 1, 551–558. Retrieved from https://journal.unnes.ac.id/sju/index.php/prisma/article/view/20142