The Amarakosha written by Amar Simha is a thesaurus of Sanskrit and is at number 100 in the list of most influential books in Indian history. The word “Amarkosha” derives from the Sanskrit words amara (“immortal”) and kosha (“treasure or dictionary”). It is also known as nama-linga-anu-shasana “instruction concerning nouns and gender”.
It is the oldest extent kosha. The author himself mention 18 prior works, but they have all been lost. There have been more than 40 commentaries on the Amarakosha.
Amarakosha, the Sanskrit thesaurus developed in 4th CE has influenced modern lexicographic techniques in quite the same way as Panini has done to generative linguistics.Amarakosha is written in verse format. He was a distinguished scholar, one among the nine “gems” (navaratna) during Vikramaditya’s court (in about 380 A. D.) (Vikramaditya was originally known as Chandra Gupta II. He was a heroic king and is well known for developing an independent calendar, widely recognized in India as Vikram Samvat). These were the great writers who produced lasting works of Sanskrit literature that sparkled in the Golden Age of India. Chief of these was Kalidasa, “India’s Shakespeare”
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.
Svargadhikanda, the first Kandam of Amarakosham begins with the verse ‘Svaravyam swarganakathridivatrishalaya..’ describing various names of Heaven viz. Sva, Avya, swarga, Naka, Tridiva, Tridasalaya etc. The second verse ‘Amara, nirjara, deva,’ describes various words that are equivalent to word God. The fifth and sixth verses give various names of Gautama Buddha. The following verses give the different names of Brahma, Vishnu, Vasudeva, Balarama, etc. All these names are treated with great reverence which makes it difficult to ascertain Amara Sinha’s theological bent.
The second Kandam, Bhuvargadhikanda, of Amarakosham is divided into ten Vargas or parts. The ten Vargas are Bhuvarga (Earth), Puravarga (Towns or Cities), Shailavarga (Mountains), Vanoshadivarga (Forests and medicines), Simhadivarga (Lions and other animals), Manushyavarga (Mankind), Bramhavarga (Brahmin), Kshatriyavarga (Kshatriyas), Vysyavarga (Vysyas) and Sudravarga (Sudras).
The Third Kandam, Samanyadhikanda contains Adjectives, Verbs, words related to prayer and business etc. The first verse Kshemankaroristatathi Shivathathi Shivamkara gives the Nanarthas of the word Shubakara or propitious as Kshemankara, Aristathathi, Shivathathi and Shivamkara.
It contains 10,000 words, and is arranged, like other works of its class, in metre, to aid the memory. The first chapter of the Kosha was printed at Rome in Tamil character in 1798. An edition of the entire work, with English notes and an index by HT Colebrooke appeared at Serampore in 1808. The Sanskrit text was printed at Calcutta in 1831. A French translation by ALA Loiseleur-Deslongchamps was published at Paris in 1839.  Louie Rice compiled the Kannada version of it and its available 4th edition was printed in 1927 which contains three khandas and 25 sargas.
The Amarakosha consists of verses that can be easily memorized. It is divided into three khandas or chapters. The first, svargadi-khanda (“heaven and others”) has words pertaining to gods and heavens. The second, bhuvargadi-khanda (“earth and others”) deals with words about earth, towns, animals and humans. The third, samanyadi-khanda (“common”) has words related to grammar and other miscellaneous words.
It is of great interest to note that, though the production of a Buddhist, it has been universally accepted as an authority by the Brahmans and the Jainas alike. The fact that it has been commented upon by Buddhists like Subhutichandra, by Jainas like Asadharapandita and Nachiraja,and by Brahmans like Kshirasvamin, Mallinatha and Appayyadikshita testifies to its usefulness to every class of Sanskrit students. It is a well-known fact that translations of the Amarakosha into Chinese and Thibetan have been recently discovered.
Amarakosha (the famous Sanskrit synonym lexicon compiled by Amarasimha) mentions seven types of riṣis : Shrutarshi, Kāndarshi, Paramarshi, Maharshi, Rājarshi, Brahmarshi and Devarshi. Amarakosha strictly distinguishes Rishi from other types of sages, such as sanyāsi, bhikṣu, parivrājaka, tapasvi, muni, brahmachāri, yati, etc.
Main article: Amara Sinha
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.
Amara Sinha (c. CE 375) was a Sanskrit grammarian and poet, of whose personal history hardly anything is known.
He is said to have been “one of the nine gems that adorned the throne of Vikramaditya,” and according to the evidence of Xuanzang, this is the Chandragupta Vikramaditya (Chandragupta II) that flourished about CE 375.Other sources describe him as flourishing in c. CE 700.
Most of his work was destroyed, with the exception of what is the celebrated Amara-Kosha (Treasury of Amara), a vocabulary of Sanskrit roots, in three books, and hence sometimes called Trikanda or the “Tripartite”.  It is also known as “Namalinganushasana”. Amara Sinha is an eminent poet and the author of Amara Kosha. He was a poet in Vikramaditya’s court. He was one of the nine gems as the poets of the king’s court were regarded. Unfortunately, he held the principles of a heterodox sect. His poems perished in the maltreatments generated by intolerant philosophers against the persons and writings of both Jainas and Buddhists
Amarakosa, Amarasinha’s Sanskrit thesaurus well-known to every Sanskrit student, is the oldest work of the kind now extant. According to tradition Amarasimha was one of the nine distinguished men (nava ratna) of the court of King Vikramaditya (4th Century CE).
Navaratnas 9 Gems of Vikramaditya’s Court
Navaratnas in Vikramaditya’s court are the 9 Main Ministers in the Raaj Sabha of Emperor Vikramaditya. They are called Navaratnas or nine gems because of their extraordinary knowledge which helps his court for the smooth functioning of the administration.
Nine Gems or Navaratnas in Vikramaditya Court
1) Vetala Bhatta – a Maga Brahmin, noted for his work of the sixteen stanza Niti Pradeepa or the Lamp of Conduct.
2) Dhanvantari – A great Ayurvedic physician
3) Varahamihira – A renowned astronomer, mathematician, and astrologer. Varahamihira’s main work is the book Pancasiddhantika or Pancha Siddhantika. Varahamihira is also known as Varaha or Mihir.
4) Vararuchi – A famous grammarian and Sanskrit scholar. Prakrita Prakasa the oldest treatise on the grammar of Prakrit language is believed to be written by Vararuchi.
5) Amarasimha – A noted Sanskrit grammarian and poet. Amara Sinha is the author of Amara Kosha (Amarkosha) a vocabulary of Sanskrit roots, synonyms and homonyms.
6) Kalidasa – Renowned Classical Sanskrit writer famous for his works Malavikagnimitram, Vikramorvasiyam and Abhignanasakuntalam.
7) Kshapanaka – One of the renowned ancient astrologers
8) Shanku –An expert in the field of architecture
9) Ghatakarpura – Ghatakpar was expert in sculpture and architecture
In antiquity, Philo of Byblos authored the first text that could now be called a thesaurus. In Sanskrit, the Amarakosha is a thesaurus in verse form, written in the 4th century.
The oldest known dictionaries were Akkadian Empire cuneiform tablets with bilingual Sumerian–Akkadian wordlists, discovered in Ebla (modern Syria) and dated roughly 2300 BCE. The early 2nd millennium BCE Urra=hubullu glossary is the canonical Babylonian version of such bilingual Sumerian wordlists. A Chinese dictionary, the c. 3rd century BCE Erya, was the earliest surviving monolingual dictionary; although some sources cite the c. 800 BCE Shizhoupian as a “dictionary”, modern scholarship considers it a calligraphic compendium of Chinese characters from Zhou dynasty bronzes. Philitas of Cos (fl. 4th century BCE) wrote a pioneering vocabulary Disorderly Words (Ἄτακτοι γλῶσσαι, Átaktoi glôssai) which explained the meanings of rare Homeric and other literary words, words from local dialects, and technical terms. Apollonius the Sophist (fl. 1st century CE) wrote the oldest surviving Homeric lexicon. The first Sanskrit dictionary, the Amarakośa, was written by Amara Sinha c. 4th century CE. Written in verse, it listed around 10,000 words. According to the Nihon Shoki, the first Japanese dictionary was the long-lost 682 CE Niina glossary of Chinese characters. The oldest existing Japanese dictionary, the c. 835 CE Tenrei Banshō Meigi, was also a glossary of written Chinese. A 9th-century CE Irish dictionary, Sanas Cormaic, contained etymologies and explanations of over 1,400 Irish words. In India around 1320, Amir Khusro compliled the Khaliq-e-bari which mainly dealt with Hindvi and Persian words