An Error analysis on grammatical structures of the studenst'theses

The research is aimed at finding out the types of the errors and their causes. The writer focuses his research on the errors of the grammatical structures based Surface Strategy Taxonomy which occur in the students� theses. It is a descriptive analytic method which analyzes the data by identifying the types of the errors, defining them, explaining them and their sources, reconstructing them into the target language and putting all of the data collected in a table form. The research finding shows that, from the three texts, there are 185 errors and there are four types of errors: omission, addition, misformation and misordering. Omission is the errors that most often occur: they are 80 errors in which 37 errors are caused by mother-tongue influence and 43 are caused by target language (learning strategy). The next errors which often occur are misformation: they are 69 errors and all of them are caused by target language (learning strategy). The next is addition. It is 25 errors: all of those are caused by target language (learning strategy). The last is misordering which is 9 errors and all of them are caused by target language (learning strategy). Thus, it can be concluded that there are serious problems. They can be the students themselves who study less, wrong learning strategy or even the teachers who do not provide proper teaching materials and methods. Because of those, the writer suggests that the students learn hard and practice more whether in the classes or out the classes because learning English basically is practice and the teachers provide proper teaching materials and methods because they are one of the instruments which can reduce the errors