The present study investigates the conceptions of infinity of students in some official secondary schools. A questionnaire was administrated to a group of 215 students of grade 10 and 11. After checking the presentation of infinity in the Lebanese curriculum, a comparative study was made between the two grades. Results showed that the majority of students conceptualize infinity as endless or huge number. Students hold misconceptions in differentiating between infinite and innumerable and in relating the infinite to unbounded. APOS results showed a strong association between process and object thinking and showed that students’ APOS levels vary according to the context in which infinity is given.

Keywords : Infinity, Misconception, APOS Theory, Curriculum, Actual and Potential Infinity.