The Amarakosha (IAST: Amarakośa) is a thesaurus of Sanskrit written by the ancient Indian scholar Amarasimha. It is the oldest extant kosha. The author himself mentions 18 prior works, but they have all been lost. There have been more than 40 commentaries on the Amarakosha.
The word "Amarakosha" derives from the Sanskrit words amara ("immortal") and kosha ("treasure, casket, pail, collection, dictionary"). The Amarakosha is also known as the Namalinganushasana (IAST: Nāmaliṅgānuśāsanam) from nāma-liṅga-anuśāsana, "instruction concerning nouns and gender".
Amarasimha is said to have been one of the Navaratnas ("nine gems") at the court of Chandragupta II, a Gupta king who reigned around AD 400. Some sources indicate that he belonged to the period of Vikramaditya of 7th century.
Mirashi examines the question of the date of composition of Amarakosha. He finds the first reliable mention in Amoghavritti of Shakatayana composed during the reign of Amoghavarsha(814-867CE)
The Amarakosha consists of verses that can be easily memorized. It is divided into three khāṇḍas or chapters. The first, svargādi-khāṇḍa ("heaven and others") has words pertaining to gods and heavens. The second, bhūvargādi-khāṇḍa ("earth and others") deals with words about earth, towns, animals and humans. The third, sāmānyādi-khāṇḍa ("common") has words related to grammar and other miscellaneous words.