This paper considers the questions of translatability and expressive power. It is argued that truthconditional content is always translatable, and does not produce differences in expressive power. Most nontruth-conditional content-presupposition, 'side effects' such as anaphora, and conventional implicature-is shown to not always translate successfully, but still not to produce genuine differences in expressivity. This last property appears to clearly hold only of terms which introduce expressive content: only for such content is genuine incommensurability found in natural language. Some implications of these findings are discussed.