The Amarakosha is a thesaurus of Sanskrit written by the ancient Indian scholar Amarasimha. The word "Amarkosha" (Sanskrit: अमरकोश, IAST: Amarakośa) derives from the Sanskrit words amara ("immortal") and kosha ("treasure, casket, pail, collection, dictionary"). It is also known as Namalinganushasana (Sanskrit: नामलिङ्गानुशासनम्, IAST: Nāmaliṅgānuśāsanam) from nama-linga-anu-shasana "instruction concerning nouns and gender".