חומש – The five books of the Torah, the first five of Tanach: Bereshit, Shemot, Vayikra, Bemidbar, and Devarim (as we call them today); in English, via Greek and Latin: Genesis, Exodus, Leviticus, Numbers, and Deuteronomy. On other terms used for Chumash and its books, see my Introduction to Sefer Bereshit.
As the Written Torah (תורה שבכתב), the words of these five books have the highest degree of sanctity, in distinction to those books composed by prophecy (Neviim, or Prophets) and by ruach ha-kodesh (Ketuvim, or Writings).
Printed Chumashim are generally divided by sidra, more commonly called parashah (or parsha), followed by the haftarah, and sometimes include the five megillot as well. Many will include the Targum and Rashi’s commentary.
On the annual cycle, today the most common reading cycle, the entire Chumash is read every year. It is divided into 54 sedarim or parshiyot, some of which are conventionally doubled in most years to allow for them to be read from one Simchat Torah to the next.