كتاب
kitāb
The word for “book” in Arabic, used for the Quran, for earlier scripture and for God’s record of all things.
What it means
The Quran is “the Book, in which is no doubt” (2:2). It speaks of God sending scripture to earlier prophets, such as the Torah to Moses and the Gospel to Jesus (3:3–4), and of the “Mother of the Book” (43:4), the source. Believers have faith in the books of God (2:285). The record of deeds is also a kitab (18:49).
What the sources say
Some scholars of Arabic think the word came from Aramaic or Akkadian roots; Muslims scholars note that Arabic has borrowed words, as other languages do, and that this does not alter its meaning.
Term and Arabic as listed in Ismail al Faruqi, Toward Islamic English (International Institute of Islamic Thought, 1995), p. 45, listed as KITĀB. The definition is restated here.