A classic Greek lexicon useful for every theology student. Note that Thayer was a universalist, so be careful with any word dealing with salvation, and also the Trinity (his definition of “Christ” would seem to doubt Jesus’ deity). Basically the majority of his word definitions are from standard usage in the Greek NT and classical literature, so in theologically charged words, be careful.
Brown-Driver-Briggs plus Thayers is a compilation of various authors of Old Testament Hebrew and New Testament Greek lexicons.
Strong Diccionario Griego y Hebreo al Español
Mounce Concise Greek-English Dictionary of the New Testament
Trench’s Classic work, Synonyms of the New Testament, is a study of Greek synonyms in the New Testament, showing their similarities and differences.
Green Greek English Lexicon
A Manual Greek Lexicon of the New Testament + Keyed to Strong’s.
Hebrew/Greek Synonym Dictionary is a dictionary module showing the Hebrew to English or Greek to English root words.
Hebrew/Greek Synonym Dictionary 1.0
Liddell Scott Greek-English Lexicon is a classic work for those who study Greek. This focuses on classical Greek as a comparison of Biblical Greek.