Parallel text

A parallel text is a text placed alongside its translation or translations. Parallel text alignment is the identification of the corresponding sentences in both halves of the parallel text. The Loeb Classical Library and the Clay Sanskrit Library are two examples of dual-language series of texts. Reference Bibles may contain the original languages and a translation, or several translations by themselves, for ease of comparison and study; Origen's Hexapla (Greek for "sixfold") placed six versions of the Old Testament side by side. A famous example is the Rosetta Stone, whose discovery allowed the Ancient Egyptian language to begin being deciphered. Large collections of parallel texts are called parallel corpora (see text corpus). Alignments of parallel corpora at sentence level are prerequisite for many areas of linguistic research. During translation, sentences can be split, merged, deleted, inserted or reordered by the translator. This makes alignment a non-trivial task. Parallel texts may be used in language education. Parallel corpora can be classified into four main categories: A parallel corpus contains translations of the same document in two or more languages, aligned at least at the sentence level. These tend to be rarer than less-comparable corpora. A noisy parallel corpus contains bilingual sentences that are not perfectly aligned or have poor quality translations. Nevertheless, most of its contents are bilingual translations of a specific document. A comparable corpus is built from non-sentence-aligned and untranslated bilingual documents, but the documents are topic-aligned. A quasi-comparable corpus includes very heterogeneous and non-parallel bilingual documents that may or may not be topic-aligned. Large corpora used as training sets for machine translation algorithms are usually extracted from large bodies of similar sources, such as databases of news articles written in the first and second languages describing similar events. However, extracted fragments may be noisy, with extra elements inserted in each corpus.