This study analyzes conversation protocols recorded during lessons in order to investigate the processes by high-school students comprehend unfamiliar vocabulary. Whenever students encounter items of unfamiliar vocabulary while reading critical essays in class, in addition to obviously consulting dictionaries, students also continue reading texts by sharing vocabulary information with other student and by attempting to describe the meaning in either more abstract or more concrete expressions in order to establish the appropriate meaning for the given context. Before the students studies the critical essays from the textbook in class, 86 of the words (33%) were known by less than 60% of the students. However, after training in vocabulary learning, the number of students who understood the appropriate meaning increased significantly for all the previously unknown vocabulary.