Pali-English Dictionary by T. W. Rhys Davids & William Stede (1921) — Probably, the most scholarly Pāḷi dictionary. Rhys Davids and Stede use the traditional alphabetical order from India. One difficulty for the amateur is the Pāḷi alphabetical order which must be memorized or written on your bookmark.
From the dust jacket:— As the Pali Text Society began issuing editions of the Pāli Canon and Commentaries in quick succession, Rhys Davids conceived the idea of an exhaustive dictionary of Pāḷi, based on the voluminous basic material that was being brought to light. The work took more than twenty years of devoted labour, but, before his death in 1922, Rhys Davids had the satisfaction of seeing its first volume published. In four volume, issued over 1921–1925, the Dictionary contains every Pāḷi word, with its Sanskrit root identified and meanings given in English. Carrying over 150,000 textual references, the work holds the field, even today, as the best Pāḷi-English dictionary. See Foreword to Pali-English Dictionary by T W Rhys Davids. To purchase this volume.
A Dictionary of the Pāḷi Language by Robert Caesar Childers — This is my favorite Pāḷi source — Why? It is in Roman alphabetical order.
It is somewhat hard to realize, seeing how important and valuable this work has been, that when in 1872 Childers published the first volume of his Pāḷi Dictionary, he only had at his command a few pages of the canonical Pāḷi books. [TW Rhys Davids]
From the dust jacket:— The Pāḷi language is one of the Prakrit or Aryan vernaculars of ancient India. It was spoken in the sixth century before Christ and great many Buddhist scriptures were written in this language. The existing Pāḷi literature is of great extent and importance. It is valuable alike to the philologist, the historian, and the students of folklore and comparative religion.
The first edition of A Dictionary of the Pāḷi Language appeared in 1875. In this monumental work by the great scholar, Robert Caesar Childers, we find a number of linguistic evidences, which consist of an analysis of words in the form and use of tenses, of syntax and of vocabulary. Moreover, we find a great number of examples and sentences using single words. Many words are miniature essays and are extremely useful and helpful to read and understand the early Buddhist treatise.
It was indeed a gratifying experience for the publishers [Cosmo Publications, Delhi 1979] to have undertaken the reprint of this most valuable reference work on Pāḷi language and it is hoped that it will serve the scholarly needs of not only students and scholars of this language but others, as well, in understanding the early Buddhist scriptures. See Preface to A Dictionary of the Pali Language by RC Childers. This volume is in print under several covers; new and used copies can be easily found using Google book search
Buddhist Dictionary by the Venerable Nyanatiloka Thera (1952) — This is a personal favourite of mine. It is not just a dictionary, but a collection of erudite essays, some several pages long. Unlike the previous two mentioned dictionaries, this book deals only with doctrinal terms. First published in 1952, it has become a standard for the Buddhist Publication Society. See Preface to Buddhist Dictionary Ven Nyanatiloka 1952. To purchase.
English-Pāḷi Dictionary by Aggamahāpaṇḍita A. P. Buddhadatta Mahāthera (1955) This publication, published by the Pali Text Society in Roman script, was considered a notable event in the life of the Society. This is a considerably enlarged form of a Concise English-Pāḷi Dictionary compiled by the author during the Second World War The author has coined many new words and has given more than one Pāḷi word for some English verbs which do not exist in ancient languages like Pāḷi. This dictionary, though not an exhaustive one, has proved very useful to scholars of the Pāḷi language as it presents well chosen material in a single volume of a manageable size. See Front pages to Buddhadatta. To purchase.
By the same Author:— The Concise Pali-English Dictionary has been prepared mainly for use by students in schools and colleges. The author is not only an eminent Elder of the Buddhist Order but one of the leading Pāḷi scholars recognized both in the East and the West as an authority on the subject. It is to be observed that the author has kept more or less to the traditional sense of words while not altogether ignoring the meanings given by western scholars in their translations and lexicons. Many errors in the latter sources have also been rectified. But the basic sense adopted is in nearly every instance the traditionally accepted meaning in accord with the commentaries and the glossaries. This perhaps is of special value to beginners as thereby they get introduced to the indigenous tradition, thus providing a useful basis on which to build up a more scientific knowledge as the study advances. To purchase