If you are looking for a high-quality PDF to download and study, these three are the "gold standard" in the field: Monier-Williams: A Sanskrit-English Dictionary
The "story" of these dictionaries is one of transitioning from ancient verse-based lexicons to modern, student-friendly alphabetical formats. Ancient Roots: Historically, Sanskrit meanings were preserved in (thesauri), the most famous being the Amarakosha english sanskrit dictionary pdf