According to the linguistic theory of "natural order," eight English morphemes have been ranked in an invariant order of difficulty for learners of English as a Second Language (ESL). Pedagogical implications of this theory have led to the "natural approach" as a comprehensive second language teaching methodology. A case study that suggests the natural order theory has limited predictiveness, because it does not consider the pragmatic salience of these morphemes in different discourse contexts, is presented. Subjects were five native Arabic-speaking adult women at an intermediate level of ESL study. In a speaking task involving extended turns, the subjects' patterns of error for the eight were analyzed. Results indicate an order of relative morpheme difficulty suggesting that pragmatic salience comprises a balance of at least four features: frequency; form-function transparency; conspicuousness; and usefulness. The implication for ESL instruction is that to make teaching effective, language instructors must consider the specific, different learning tasks involved in the different kinds of discourse to which the student is exposed. (Author/MSE)