Book
Standard dictionaries for reading the Quran’s Arabic: Lane’s Lexicon, Hans Wehr, and the classical Lisān al-ʿArab.
What it means
Edward William Lane’s Arabic-English Lexicon (eight volumes, 1863–93) is based on classical Arabic dictionaries, mainly the Tāj al-ʿArūs. Hans Wehr’s Dictionary of Modern Written Arabic is a smaller one in wide use. The classical Lisān al-ʿArab of Ibn Manzur (d. 1311) is the great Arabic dictionary of the Arabic language.
What the sources say
A reader of the Quran in English needs a lexicon, because many Quranic words have a range of meanings that translations choose among. This site gives the commentators’ range where it matters.