From Innerpedia - Encyclopedia of Torah's Inner Dimension - Chassidut and Kabbalah
The number zero is translated in modern Hebrew as (efes).
In number theory
In the Bible
The word efes appears a few dozen times in the Bible. Its meaning in the Bible revolves around the verb "to nullify".
In the Sages
As a number, zero is first alluded to in Sefer Yetzirah (Book of Formation) in the words: "Before one, what do you count?" This statement implies that zero is different from other numbers, in that it is a concealed rather than a revealed entity. Thus, the relationship of zero to other numbers is a concealment-revelation one.
In Kabbalah as explained in Chassidic teachings, the modern Hebrew word אפס (efes) is part of a triad of related terms: efes (אפס), ayin (אין), tohu (תהו), which can be translated as zero, nothingness, and chaos. This triad corresponds to the three heads of the crown respectively, and thus zero corresponds to the highest head, radla.