Amarakosa is the most renowned Sanskrit lexicon, memorized by a traditional Indian student when introduced to Sanskrit. The beauty is in the way the words are organized - in verse and as a thesarus where words for the same concept are grouped together and related concepts follow each other. To add to this, the work also tells us about the gender of the nouns. All this makes it easy for the traditional pandit who has studied the amarakosa to easily read Sanskrit texts without needing to keep referring to a dictionary. This facilitates the better recognition of subtle word meanings and reading flow, compared to the modern student who needs to breaking her reading to refer to a dictionary and is often confused as to which meaning to adopt.
For some adult learners, understanding the structure and scope of the amarakosa can aid in planning their study better. So here is a summary of amarakosa by the numbers:
1) As explained in [1], amarakosa has 11,580 words.
2) However, some words are repeated since they stand for different concepts. e.g. rauhiNeya is the word for both balarAma and budha (mercury). We therefore have a total of 9031 unique words.
3) These words belong to 1407 synonym sets (synsets). For e.g. siva (the bhagavAn) is one synset comprising 52 words in 5.5 sloka-s, the first of which (comprising 11 words) is:
शम्भुरीश: पशुपति: शिव: शूली महेश्वर: ।
ईश्वर: शर्व ईशान: शङ्कराश्चन्द्रशेखर: ॥ I.30 ||
Another synset example is that of "cloud" which has 15 names arranged in 1.5 sloka-s as follows:
अभ्रं मेघो वारिवाह: स्तनयित्नुर्बलाहक: ।
धाराधरो जलधरस्तडित्वान् वारिदोऽम्बुभृत् ॥
घनजीमूतमुदिरजलमुग्धूम्योनय: ।
3) The 11,580 words are organized in 1550 sloka-s; as per the Sardesai-Padhye book [2] that I follow.
Incidentally, [1] mentions 1608 sloka-s. Even with [2], i get a few discrepancy in counts (say, 2 sloka-S in a kAnDa) but since these are marginal so i do not describe the differences.
4) The sloka-s are distributed in 25 varga-s (chapters)
(i'm counting the vyoma and dik varga-s in the 1st kanDa as two separate. Not sure if they're sub-parts of one vyoma-dik varga)
5) These 25 varga-s are classified into 3 parts (kAnDA-s).
6) Here is a frequency distribution of the slokA-s by varga. This is useful as one learns and wants to track progress. The traditional approach, AFAIK, is not to keep quantitative track at all but just keep a set time and duration every single day without fail - eventually you are bound to reach the destination.
[2] classifies sloka-s as mUla and kSepaka. Am not sure how this is arrived at (possibly due to development of a 'critical edition') but my understanding is that the kSepaka sloka-s are thought to be later additions not belonging to the original. In [2], kSepaka slokas account for a small 3.7% of all the sloka-s. In one Hindi translation of the amarakosa, these sloka-s are called prakSipta sloka-s.
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How long does it take to memorize the amarakosa? This obviously would vary by circumstance (full-time pathasala student vs part-time sanskrit learner) but [1] gives a range of 6 months to a year. Taking the outer limit, this would mean memorizing 4.4 slokas, on average. This isn't too difficult - especially if you are starting young. But then one also needs to take into account time to review previous lessons, holidays etc. [2] in their introduction, talk of students (in the 'modern' education mode) studying the amarakosa in grades IV to VII. This means studying it across four years from the ages of 9 to 12; just one sloka a day on average!
Our tradition is primarily one of intense oral knowledge transmission. Such being the case, traditionalists are extremely comfortable with memorizing, and later cross-referencing and intellectually playing with that information in their head. They never get intimidated with works even more than a 1000 verses long such as the amarakosa; they have several such works memorized. The advent of western methods of teaching have its benefits but a huge drawback has been that students get intimidated with memorizing even, say, 100 sloka-s. So sri mahAdeva sivarama goLe brought out an amarasAra (an abridgement of the amarakosa) and, in the introduction, says something to the effect that it is impossible for a student to memorize the full work with all the activities that students are involved in 'nowadays' (100 years ago!). Practical experience goes against this statement. It is very much possible - even essential - to memorize and study the whole amarakosa, if one is a serious Sanskrit student. AFAIK, in the ideal traditional setting, a young student first learns the viSNu sahasranAma (beginning, say, at the age of three if the pronunciation is good) and then move onto the amarakosa so that this is memorized by the time the child is about six/seven.
I met a Sanskrit professor some years ago and she was saying she still studies the amarakosa (she was about 55 when i met her). So no despair if one is 'old'. Start!
References:
[1]
The Knowledge Structure in Amarakośa. Nair, Sivaja S., Kulkarni, Amba.
Sanskrit Computational Linguistics, Volume 6465 of the series Lecture Notes in Computer Science, 2010, pp 173-189
[2] amarA's nAmaliMgAnusAsanam, Dr. N.G.Sardesai and D.G.Padhye, Oriental Book Agency, Poona, 1940