The core of the Tanakh (the Hebrew Bible) is written in Classical Hebrew, and much of its present form is specifically in the dialect of Biblical Hebrew that scholars believe flourished roughly around the 6th century BCE, near the Babylonian Exile. In light of this fact, Jews have called Hebrew the "language of Holiness" (Leshôn Ha-Kôdesh) since ancient times.
Most linguists agree that after the 6th century BCE when the Neo-Babylonian Empire destroyed Jerusalem and exiled its population to Babylon and the Persian Empire allowed them to return, the Biblical Hebrew dialect prevalent in the Bible came to be replaced in daily use by new dialects of Hebrew and a local version of Aramaic.
After the 2nd century CE when the Roman Empire exiled the Jewish population of Jerusalem and parts of the Bar Kochba State, Hebrew gradually ceased to be a spoken language roughly around 300 CE, but remained a major literary language during the centuries since. Not only was it used for religion, but for a large variety of purposes. Letters, contracts, commerce, science, philosophy, medicine, poetry, justice codes, all resorted to Hebrew, which thus adapted to various new fields and terminologies by borrowings and inventions.
Hebrew was revitalized during the late 19th and early 20th century as the spoken language of Israel, called Israeli Hebrew or Modern Hebrew. Eventually it replaced a score of languages spoken by Jews at that time, such as Ladino (also called Judezmo), Yiddish, Russian, and other languages of the Jewish diaspora.
Because of its large disuse for centuries, Hebrew lacked many modern words. Several were adapted as neologisms from the Hebrew Bible or borrowed from other languages by Eliezer Ben-Yehuda. Largely because of this, modern Hebrew became an official language in British-ruled Palestine in 1921 (along with English and Arabic), and the primary official language of the State of Israel.