Abstract: One of the most significant and enthralling aspects of human development is language development. This study presents learners attempts at constructing a linguistic system that progressively approach the target language system. This process is call as Interlanguage. The focus of this study is on one of interlanguage characters, it is permeability. Permeability reflects the students native language transfer and overgeneralization in their efforts to produce the intended meaning in target language. The objective of this study is to present observed proves of the permeability of the students’ interlanguage by describing the types of influence from the native and target language and presenting the what causes this influence. The data were collected from erroneous sentences taken from students composition.