It is important for teachers to raise awareness about the differences between L1 (Thai) and L2 (English) in terms of derivations. The stem of a Thai word is changed to other derivatives by adding a prefix, e.g. /sueksa/ (= v.; educate), /kan sueksa/ (= n.; education), /nak kan sueksa/ (= n.; educator); on the other hand, the stem of an English word is usually changed to other derivatives by adding a suffix, e.g. educate, education, or educator.