A bilingual ictionary is a dictionary that is usually used to translate words or phrases from one language to another. Bilingual dictionaries are sometimes used to understand texts read, often, in a foreign language. Bilingual dictionaries can be unidirectional, meaning that they list the meanings of words of one language in another, or can be bidirectional, allowing translation to and from both languages. Bidirectional bilingual dictionaries usually consist of two sections, each listing words and phrases of one language alphabetically with their translation. Other features sometimes present in bilingual dictionaries are definitions, lists of phrases, usage and style guides, verb tables and maps. The Mahāvyutpatti (Wylie: Bye-brtag-tu rtogs-par byed-pa chen-po), The Great Volume of Precise Understanding or Essential Etymology, was compiled in Tibet during the late eighth to early ninth centuries CE, providing a dictionary composed of thousands of Sanskrit and Tibetan terms designed as means to provide standardised Buddhist texts in Tibetan, and is included as part of the Tibetan Tangyur (Toh. 4346). It is the earliest substantial bilingual dictionary known.