Romanization (also spelled romanisation: see spelling differences), in linguistics, is the conversion of writing from a different writing system to the Roman (Latin) script, or a system for doing so. Methods of romanization include transliteration, for representing written text, and transcription, for representing the spoken word, and combinations of both. Transcription methods can be subdivided into phonemic transcription, which records the phonemes or units of semantic meaning in speech, and more strict phonetic transcription, which records speech sounds with precision.
There are many consistent or standardized romanization systems. They can be classified by their characteristics. A particular system’s characteristics may make it better-suited for various, sometimes contradictory applications, including document retrieval, linguistic analysis, easy readability, faithful representation of pronunciation.
If the romanization attempts to transliterate the original script, the guiding principle is a one-to-one mapping of characters in the source language into the target script, with less emphasis on how the result sounds when pronounced according to the reader's language. For example, the Nihon-shiki romanization of Japanese allows the informed reader to reconstruct the original Japanese kana syllables with 100% accuracy, but requires additional knowledge for correct pronunciation.
Most romanizations are intended to enable the casual reader who is unfamiliar with the original script to pronounce the source language reasonably accurately. Such romanizations follow the principle of phonemic transcription and attempt to render the significant sounds (phonemes) of the original as faithfully as possible in the target language. The popular Hepburn romanization of Japanese is an example of a transcriptive romanization designed for English speakers.