Nida has been a pioneer in the fields of translation theory and linguistics.
His Ph.D. dissertation, A Synopsis of English Syntax, was the first full-scale analysis of a major language according to the "immediate-constituent" theory. His textbook Morphology: The Descriptive Analysis of Words was one of the major works of American Structuralism. It remained the only thorough introduction to the field for decades and is still valuable for its many examples and exercises.
His most notable contribution to translation theory is Dynamic Equivalence, also known as Functional Equivalence. For more information, see "Dynamic and formal equivalence." Nida also developed the componential analysis technique, which split words into their components to help determine equivalence in translation (e.g. "bachelor" = male + unmarried). This is, perhaps, not the best example of the technique, though it is the most well-known.
Nida's dynamic-equivalence theory is often held in opposition to the views of philologists who maintain that an understanding of the source text (ST) can be achieved by assessing the inter-animation of words on the page, and that meaning is self-contained within the text (i.e. much more focused on achieving semantic equivalence).
This theory, along with other theories of correspondence in translating, are elaborated in his essay Principles of Correspondence,[6] where Nida begins by asserting that given that "no two languages are identical, either in the meanings given to corresponding symbols or in the ways in which symbols are arranged in phrases and sentences, it stands to reason that there can be no absolute correspondence between languages. Hence, there can be no fully exact translations." [7] While the impact of a translation may be close to the original, there can be no identity in detail.
Nida then sets forth the differences in translation, as he would account for it, within three basic factors:
The nature of the message: in some messages the content is of primary consideration, and in others the form must be given a higher priority.
The purpose of the author and of the translator: to give information on both form and content; to aim at full intelligibility of the reader so he/she may understand the full implications of the message; for imperative purposes that aim at not just understanding the translation but also at ensuring no misunderstanding of the translation.
The type of audience: prospective audiences differ both in decoding ability and in potential interest.