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Old Testament / Hebrew Bible essential language tools
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Gesenius' Hebrew GrammarGesenius' Hebrew Grammar by H. F. W. Gesenius
Buy new: $59.46 / Used from: $23.00
Still the standard reference grammar for Biblical Hebrew
Brown-Driver-Briggs Hebrew and English LexiconBrown-Driver-Briggs Hebrew and English Lexicon by Francis Brown
Buy new: $23.07 / Used from: $16.45
By far the best 1 volume dictionary
A Grammar of Biblical Hebrew: 2 Volume Set. Vol. 1, Part 1. Orthography And Phonetics; Part 2. Morphology. Vol. 2,  Part 3 Syntax (Subsidia Biblica, 14/1-14/2)A Grammar of Biblical Hebrew: 2 Volume Set. Vol. 1, Part 1. Orthography And Phonetics; Part 2. Morphology. Vol. 2, Part 3 Syntax (Subsidia Biblica, 14/1-14/2) by Paul Jouon
Buy used from: $70.00
With Gesenius, the only reference grammar worth owning
An Introduction to Biblical HebrewAn Introduction to Biblical Hebrew by Thomas O. Lambdin
Buy new: $82.72 / Used from: $52.78
Best introductory grammar.  Paperback available in UK.
An Introduction to Biblical Hebrew SyntaxAn Introduction to Biblical Hebrew Syntax by Bruce K. Waltke
Buy used from: $46.99
Like it says: great for syntax
The Hebrew and Aramaic Lexicon of the Old Testament, 2 volume setThe Hebrew and Aramaic Lexicon of the Old Testament, 2 volume set by Ludwig Koehler
Buy new: $214.20 / Used from: $199.98
Newer dictionary than BDB; accurate, but lacks some features.  Bulky.
Biblia Hebraica StuttgartensiaBiblia Hebraica Stuttgartensia by K. Elliger
Buy new: $54.59 / Used from: $23.98
The BHS: standard critical edition of the Hebrew Bible / OT
A Simplified Guide to Bhs: Critical Apparatus, Masora, Accents, Unusual Letters & Other MarkingsA Simplified Guide to Bhs: Critical Apparatus, Masora, Accents, Unusual Letters & Other Markings by William R. Scott
Buy used from: $5.99
Very helpful for understanding foot- and marginal notes in BHS
The Masorah of Biblia Hebraica Stuttgartensia: Introduction and Annotated GlossaryThe Masorah of Biblia Hebraica Stuttgartensia: Introduction and Annotated Glossary by Page H. Kelley
Buy new: $23.40 / Used from: $18.87
Help with the masoretic apparatus of BHS
Septuaginta (Greek Edition)Septuaginta (Greek Edition)
Buy used from: $31.99
Standard edition of the ancient Jewish translation of the Bible into Greek
Greek-English Lexicon of the SeptuagintGreek-English Lexicon of the Septuagint by J. Lust
Buy new: $119.99 / Used from: $49.95
The Bible In Aramaic: Based On Old Manuscripts And Printed TextsThe Bible In Aramaic: Based On Old Manuscripts And Printed Texts
Buy new: $168.00 / Used from: $153.80
Ancient Jewish translations of the Bible into Aramaic; Aramaic text only, no translations
A Dictionary of the Targumim, the Talmud Babli and Yerushalmi, and the Midrashic LiteratureA Dictionary of the Targumim, the Talmud Babli and Yerushalmi, and the Midrashic Literature by Marcus Jastrow
Buy new: $32.97 / Used from: $19.97
Great dictionary for post-biblical Hebrew & Aramaic
A grammar of Biblical Aramaic (Porta linguarum orientalium. Neue Serie)A grammar of Biblical Aramaic (Porta linguarum orientalium. Neue Serie) by Franz Rosenthal
Buy used from: $75.00
Standard grammar for the Aramaic portions of Daniel and Ezra
An Introduction to Aramaic (Resources for Biblical Study)An Introduction to Aramaic (Resources for Biblical Study) by Frederick E. Greenspahn
Buy new: $31.65 / Used from: $27.49
Newer, user-friendlier introduction to Biblical Aramaic