This study was conducted based on the reason that abstracts were very important, because they gave a first impression of the document that followed. It also showed the reader what to look for and let them decide whether to continue reading or not. An abstract should represent as much as possible the quantitative or qualitative information in the document, and also reflects its reasoning. So that, the abstract should be written clearly and correctly. If there are lots of mistakes or errors found in abstract, that is going to be questionable how the credibility of the writer is.
The purpose of this study was to find out and analyze how the students’ interlanguages were, what kinds of interlanguage errors generally students made, and what factors caused the errors. In this research, the researcher used descriptive qualitative approach.
The result of the study shows that all the students’ abstracts identified have errors. So it is clear that the students still felt difficulty in writing abstract. There are nine types of errors. The errors in the use of: Tenses (52.17%), subject-verb agreement (11.96%), sentence structure of clause (9.78%), singular-plural noun (6.52%), word order (3.27%), pronoun (1.09%), preposition (2.17%), meaning (7.61%), capitalizing (5.43%).The errors generally students made are in the use of tenses (52.17%). It means that in writing abstract, the students mostly felt difficulty in the use of tenses. It means in writing abstract the students mostly felt difficulty in the use of subject-verb agreement. The errors can be because of the interference of the first language (interlingual errors), the lack of students’ understanding on the target language (intralingual errors).