Already many scholars have given lot of useful information in this regard. Still I suggest a way which can be helpful in this context.
1. THE PRACTICAL SANSKRIT-ENGLISH DICTIONARY OF VS APTE
For meanings in English for Sanskrit words - I find more comfort in THE PRACTICAL SANSKRT-ENGLISH DICTIONARY of VS Apte than in Monier William's Dictionary.
The merits of this dictionary (VS Apte's Dictionary) -
a) Etymological notes in Sanskrit for every Subanta word is given.
b) Gender specification of all Subanta words is given enabling the learners to learn more specifically.
c) All possible shades of meanings of every word are given with illustrations from Vedas, Itihasas, Puranas, Kavyas, Sastra texts and
technical texts. This is very much useful for new and regular users to get acquainted with the practice of using the words in vogue.
d) Full explanations for all Technical words of different Sastras like - Nyaya, Vaiseshika, Vedanta, Grammar, Poetics and Dramaturgy are given with necessary illustrations.
d) All possible and popular compounds of most frequently used words are available in this dictionary.
e) While dealing with Dhatus - Dhatu, Its Gana,
Parasmaipadi/Atmanepadi/Ubhayapadi specification, Its special forms and various shades of meanings with illustrations from literature are given.
f) While dealing with Krt forms or Avyayas also their source pratyas etc. are given in detail.
In this manner VS Apte's Practical-Sanskrit Dictionary is really found practical in helping the learners.
2. Vacaspatyam -
This is a wonderful word-treasure for those who want to learn the Sanskrit-Sanskrit meanings, etymology, usages etc., Besides such features this Dictionary gives all details of the Historicity of a word giving illustrations for its usage in different sastras running through several pages. For a sincere technical learner this is an excellent source. One who regularly uses Vacaspatyam can surely become a scholar in a span of two to three years provided he uses it knowing all the technicalities of using it.
3. HALAYUDHA KOSA - (Sanskrit to Sanskrit)
This is the next useful Dictionary which I like the most. This has a peculiar style of dealing with the meanings in the following manner.
a) Etymology in Sanskrit, b) All shades of meanings c) Illustrations from literature for every usage, d) All synonyms of the Entry Word (This is the
peculiar feature of this dictionary which is not found elsewhere.)
But Dhatus and Verbs are not dealt with in this.
4. AMARAKOSA (With Kshirasvamin's Commentary)
This is an excellent source for those who want all popular synonyms of any chosen word in the Amarakosa Text and its Etymological notes in the Kshirasvamin's Vyakhyanam.
So a sincere Sanskrit learner should possess all
these four dictionaries at hand's reach.
Further also as many number of dictionaries as possible can be procured. Our Tradition callshim ACHARYA who possesses Lexicons with him (Kosavan Acharyah is the traditional observation).
Dr. Rani Sadasiva Murty