This experimental study is based on the assumption that teaching English vocabulary through Latinate word parts to undergraduate students learning English as a foreign language is an efficient means of facilitating vocabulary acquisition and also provides a useful tool for expanding the depth and breadth of lexical knowledge.

The study was carried out at the Department of English Language Teacher Training in a state university in Turkey. The participants were the freshmen students in their first semester and the senior students in their seventh semester of academic study. Freshman class was randomly divided into two in order to form the treatment and control groups, and the senior class functioned as the second control group.

A pre-test was administered to freshman students as to assess their knowledge of Latinate English words, and only the treatment group received instruction on the Latinate word parts. The semester-long teaching covered ten roots, ten prefixes and fourteen suffixes, and none of the words in the pre-test was included in the instruction program. In the course of the semester, also a mid-term and a final test were utilized to gauge the progress the treatment group students made.

At the end of the semester, the pre-test was administered once more as the post-test to both the treatment and freshman class control group students, as well as to the senior class control group participants in order to observe the effect of Latinate word-part instruction on vocabulary learning. Furthermore, interviews with the treatment group students who volunteered to take part in were carried out as to elicit their opinions on the instruction program.

The results of this study indicate a statistically significant difference between the post-test scores of the treatment and the freshman control group students which suggests that Latinate word-part instruction has a positive effect on English vocabulary acquisition. The analysis of scores obtained from the mid-term and the final tests also indicates a statistically significant increase, implying a meaningful benefit derived from the Latinate word-part instruction carried out.

Comparison of the post-test scores obtained by the treatment group students with those of the senior class control group participants who took the same test but who did not receive the same instruction suggests that explicit teaching of Latinate word-parts helps students to acquire this knowledge in advance, balancing the three years’ advancement of the senior-class members.

The analysis of student opinions obtained during the interview sessions show that treatment group students were satisfied with the Latinate word-part instruction they received. The interviewees expressed that they became cognizant of the benefits of learning vocabulary with the aid of roots and affixes, and that, as the future teachers of English, they were willing to utilize the system in both learning vocabulary themselves and also in teaching their prospective students.