(This article is submitted by Mohammad Hashamdar, PhD Student, Islamic Azad University-Science and Research Branch- Tehran- IRAN, E-mail: m_hashamdar@yahoo.com)

Second Language Acquisition has two different senses to be distinguished. Ellis (2005) classified these two senses. He referred to the first one as the learning of another language after the acquisition of one’s mother tongue is completed. He labeled it the object of inquiry. The second sense refers to the study of how people learn a second language; that is, it can be labeled as the field of enquiry.

There might be different views in scientific realms of various disciplines. Theses different views do not always lead to confrontation and debate. They may lead to separate development in that field. That field has to undergo a degree of fragmentation in which different areas of enquiry, while still under the title of the main discipline, can go for their own interest and add new discoveries. One highly dynamic area of enquiry of this kind is the field of Second Language Acquisition.
In 1960s onward, the study of First Language Acquisition was accelerated in the language domain. This acceleration in that field caused the initiation of the study in the SLA in 1970s. Cook (2003) states that SLA research concerned itself with both explaining and describing the process of acquiring a second language. At first, particular areas of interest have included the degree of transfer from the first language to the second language. Later, this transfer from first language to second changed direction and in some topic such as individual differences, the itinerary was from second language to first one. (more…)