A review of the literature in science education shows that most students have difficulties in hypothetico-deductive reasoning. The author's objective in this study was to investigate the abilities of high school teachers and university teachers to understand the difference between the terms "hypothesis" and "prediction" in the everyday context of Columbus's discovery of America. The author asked 83 high school and university teachers enrolled in a methodology course to elaborate and to explain a prediction and a hypothesis based on Columbus's discovery. Results, based on written responses, showed that most teachers (approximately 60%) did not understand the difference between a hypothesis and a prediction. The author also observed that many teachers did provide a satisfactory description of what they considered to be a hypothesis and a prediction. However, the difficulty for the teachers consisted in operationalizing (elaborating and understanding) the difference between a hypothesis and a prediction. Some teachers explicitly elaborated and classified a prediction as a hypothesis and, at times, the teachers elaborated the two terms in the same manner, without being aware of the contradiction. The study has educational implications by showing that, just like students, teachers have difficulties with the elaboration and understanding of the concepts of hypothesis and prediction. Given the importance of such concepts for all research programs, it is essential that appropriate teaching strategies be implemented. (Contains 1 table.)