Chumash (also Ḥumash; Hebrew: חומש, pronounced [χuˈmaʃ] or pronounced [ħuˈmaʃ] or Yiddish: pronounced [ˈχʊməʃ]; plural Ḥumashim) is a Torah in printed and book bound form (i.e. codex) as opposed to a Sefer Torah, which is a scroll.
The word comes from the Hebrew word for five, ḥamesh (חמש). A more formal term is Ḥamishah Ḥumshei Torah, "five fifths of Torah". It is also known by the Latinised Greek term Pentateuch in common printed editions.
The word ḥumesh is a standard Ashkenazic vowel shift of ḥomesh, meaning "one-fifth", alluding to any one of the five books; by synecdoche, it came to mean the five fifths of the Torah. The Modern Hebrew and Sephardic pronunciation ḥumash is an erroneous reconstruction based on the assumption that the Ashkenazic accent, which is almost uniformly penultimately stressed, had also changed the stress of the word. In fact, ḥumesh preserves the original stress pattern and both pronunciations contain a shifted first vowel.
In early scribal practice, there was a distinction between a Sefer Torah, containing the entire Pentateuch on a parchment scroll, and a copy of one of the five books on its own, which was generally bound in codex form, like a modern book, and had a lesser degree of sanctity. The term ḥomesh strictly applies to one of the latter. Thus, ḥomesh B'reshit strictly means "the Genesis fifth", but was misread as ḥumash, B'reshit and interpreted as meaning "The Pentateuch: Genesis", as if ḥumash was the name of the book and Bereshit the name of one of its parts. Compare the misunderstanding of "Tur" to mean the entirety of the Arba'ah Turim.
In the legal codes, such as Maimonides' Mishneh Torah, it is laid down that any copy of the Pentateuch which does not comply with the strict rules for a Sefer Torah, for example, because it is not a parchment scroll or contains vowel signs, has only the same sanctity as a copy of an individual book (ḥomesh). In this way, the word ḥomesh (or ḥumash) came to have the extended sense of any copy of the Pentateuch other than a Sefer Torah.
The word ḥumash generally only refers to "book" bound editions of the Pentateuch, whereas the "scroll" form is called a sefer Torah ("book [of the] Torah").
In modern Jewish practice:
Further information: Jewish English Bible translations