We propose a minimum learning judgment system that is appropriate for online learning environments, and we verify this minimum learning judgment system through various experiments. By focusing on the learning effort, this system can easily and quickly determine whether learners have exerted the minimum effort required for learning. To do this, the system automatically generates a word game and determines whether minimum learning has taken place through the results of the word game. To verify the minimum learning judgment system, we conducted a comparative experiment on the importance of high-frequency words, a word count verification test for word games, and a judgment criteria verification test based on the length of a video lecture. Results of the experiments show that high-frequency words can be used as a feature to determine minimum learning. The appropriate number of words in the word game for the minimum learning judgment was found to be seven, and the results showed that the video length did not affect the minimum learning criteria. In addition, the minimum learning judgment accuracy result was 82%. This is not considered very high judgment accuracy, but the accuracy of the judgment is positive considering the aim of this study.