Variability has continuously attracted interest among some second language acquisition (SLA) researchers. Attempts have been made to explain interlanguage (IL) variability by appealing to a number of different constructs, including attention to forin, planning time, linguistic context etc. A more recent attempt seeks to explain variability through the construct of discourse domain. This paper seeks to demonstrate that, although the attempt to explain variability by situating it within a discourse context is most welcome, it is not likely to be very successful since the concept is not theoretically rigorously defined. Because this definition is loose, it is difficult to distinguish the concept from more widely used concepts in language studies such as topic, genre etc. Therefore, Occam's Razor should be applied and the concept abandoned. Furthermore, evidence in support of the role of discourse domain in language variability is open to question because of a mismatch between the way the concept is defined and the methoilology used in the research.There a r e a n u m b e r of factors which have been proposed to explain interlanguage (IL) variability, including planning time, linguistic context, attention to form, automaticity, monitoring, social factorssuch as t h e nature of t h e interpersonal relationship between speaker a n d h e a r e rand the topic u n d e r discussion (EUis 1988; Taronr. 1988). Selinker and and Douglas a n d Selinker (1985) cite a n acltlitional factor, i.c. discourse domain. This paper argues that the a t t e m p t to cxplain 11, v a r i a l d i t y b y evoking t h e notion of discourse domain is most welcome l~c c a u s e of t h e importance of situating variability within discourse (whirh is p a r t of t h e effort of situating IL in context); b u t unfortunately the concept is tlefinctl in such a loose way a n d used so inconsistently t h a t a t times i t appcars to vollapse t h e distinction
