<![CDATA[ABSTRACT Mathematical conceptual understanding plays an important role in helping students connect mathematical knowledge with problem solving, including contextual problems involving triangles. This study aims to describe the mathematical conceptual understanding of low-ability junior high school students in solving contextual triangle problems based on Van Hiele Theory. This study employed a qualitative approach with a descriptive-exploratory design. Two subjects were selected through purposive sampling from Grade VIII B students at MTs Putra Putri Simo Karanggeneng based on the results of a pretest. Data were collected through a pretest, conceptual understanding tests, semi-structured interviews, and documentation, and were analyzed through data reduction, data presentation, and conclusion drawing and verification. The results showed that both subjects experienced difficulties particularly in transforming representations, recognizing the meaning and interpretation of concepts, and identifying the properties and conditions of triangle concepts. Based on the analysis results, one student (R1) was at Level 0 (visualization), while one student (R2) was at Level 1 (analysis). The study concludes that differences exist in the characteristics of conceptual understanding and geometric thinking development among low-ability students when solving contextual triangle problems. ABSTRAK Pemahaman konsep matematis berperan penting dalam membantu siswa menghubungkan pengetahuan matematika dengan penyelesaian masalah, termasuk masalah kontekstual pada materi segitiga. Penelitian ini bertujuan mendeskripsikan pemahaman konsep matematis siswa SMP berkemampuan rendah dalam menyelesaikan masalah kontekstual segitiga berdasarkan Teori Van Hiele. Penelitian menggunakan pendekatan kualitatif dengan desain deskriptif-eksploratif. Dua subjek dipilih secara purposive sampling dari siswa kelas VIII B MTs Putra Putri Simo Karanggeneng berdasarkan hasil pretest. Data diperoleh melalui pretest, tes pemahaman konsep, wawancara semi-terstruktur, dan dokumentasi, kemudian dianalisis melalui reduksi data, penyajian data, serta penarikan dan verifikasi kesimpulan. Hasil penelitian menunjukkan bahwa kedua subjek mengalami kesulitan terutama dalam mengubah representasi, mengenali makna dan interpretasi konsep, serta mengidentifikasi sifat dan syarat konsep segitiga. Berdasarkan hasil analisis, sebanyak 1 siswa (R1) berada pada Level 0 (visualization), sedangkan 1 siswa (R2) berada pada Level 1 (analysis). Simpulan penelitian menunjukkan adanya perbedaan karakteristik pemahaman konsep dan perkembangan berpikir geometris antara siswa berkemampuan rendah dalam menyelesaikan masalah kontekstual segitiga.]]>
