This paper explores sixty-six students' personal meaning and interpretation of the vertex of a quadratic function in relation to their understanding of quadratic functions in two different representations, algebraic and word problem. Several categories emerged from students' personal meaning of the vertex including vertex as maximum or minimum (highest or lowest point), vertex in relation to symmetry, vertex as a starting point or turning point, vertex as an intercept, vertex as an intersection, and miscellaneous. These categories are explored in relation to how the students were able to solve two problems, one an explicit computation, and the other a real world application problem of the vertex. The students' responses were analyzed according to the action-process-object-schema (APOS) theoretical framework (Asiala et al., 1996). Results indicate that it may be useful to explore students' personal meanings of the vertex to help them overcome conceptual obstacles, as well as to emphasize the use and application of the vertex of a quadratic function in real world problems.