Jeong, Yongkil. 2003. Extra-linguistic Effects of Feature Conflict in English. English Language and Linguistics 15, 191-212. Conflicting features between different elements in a sentence often cause the sentence to be ungrammatical. There are cases in English, however, in which feature conflict does not result in ungrammaticality. The purpose of this article is to show that feature conflict is sometimes allowed in order to produce some extra-linguistic effects. We will discuss D(eterminers) and N(ouns) in terms of (in)definiteness and show that extra-linguistic effects are produced when the definiteness features of D and N are conflicting. We will also deal with the use of the progressive aspect with frequency adverbs such as 'always' and 'continually' and show that the feature conflict between the progressive aspect and the adverbs produces some extra-linguistic effect. Key words: grammatical features, feature conflict, feature redundancy, (in) definiteness, permanency and temporariness, extra-linguistic effect