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In Nefesh HaChaim, Rabbi Chaim of Volozhin (1749-1821) (2:17) calls the “chayah” the neshamah of the neshamah. In many sources, “chayah” is paired with “yechidah.” What exactly are the chayah and the yechidah?

In Cheshek Shlomo, Rabbi Shlomo Pappenheim traces “chayah” (and “chayim”) to the two-letter root chet-yod, which means life (“chai”). He writes that chet-vav is an extension of this root and also means life. Thus, “chaveh” (Psalms 19:3 and Job 32:17) refers to speech because verbalizing something gives life to an idea that hitherto only existed in thought.


Adam’s wife was named Chava because she was the mother of all human life (Genesis 3:20). A farm is called a chavah (Numbers 32:41) because its products provide life and sustenance.

Rabbi Aharon Marcus [1843-1916] connects “chayah” to “hayah” [was, existed], explaining that living denotes the most complete form of existing.

In Yerios Shlomo, Rabbi Pappenheim traces “chayah” to the monoliteral root represented by the letter chet. He writes that this letter denotes rest, peace, harmony, or lack of strife/contradiction. “Chayah” thus connotes life as a state of equilibrium between all the components of one’s body (as life can only exist under this equilibrium).

Although “yechidah” in the sense of soul does appear anywhere in the Bible, the root chet-dalet, writes Rabbi Pappenheim, means singularity/unification. In the Bible, “yechidah” appears once (Judges 11:34), describing Jephtah’s daughter as an only child.

According to Rabbi Pappenheim, “echad” (the number one) and “yachad” (two sub-units joining as one) are also derived from chet-dalet. Additionally, “chidud” means sharp because the brunt of a sharp force focuses on one point, and “chidah” is a riddle because it requires one to sharpen one’s mind and harness all of one’s mental energies towards the resolution of a single question.

With Rabbi Pappenheim’s explanations in hand, we can better appreciate Chazal’s statements on the chayah and yechidah. The Midrash (Bereishis Rabbah 14:9) says chayah is the transcendental nature of the soul that continues to live when the physical body dies, and yechidah is the uniqueness of the soul (in that it is man’s only limb that has no counterpart).

The Vilna Gaon (1720-1797) in Aderes Eliyahu (to Genesis 2:7) writes that chayah refers to the overall holistic life-force; he also writes that man today does not have a yechidah. He will only have one in the future, in Messianic times.

The Shelah (1555-1630) writes that not everyone can be cognizant of their chayah and yechidah during their lifetimes. Only bnei aliyah (spiritually-elevated people) can connect with their chayahyechidah.

Rabbi Alexander Sender Shor (1660-1737) maintains that an ordinary person has a nefesh, ruach, and neshamah. A prophet – who attains the pinnacle of spiritual awareness – has the added elements of chayah and yechidah. Meanwhile, a sinner kills a part of himself and thus loses his neshamah. If he continues to sin, he eventually loses his ruach as well, leaving him only with a nefesh, just like an animal.

Rabbi Yaakov Yehoshua Falk (1680-1756) writes that a child receives a nefesh when he is conceived and can start moving around in utero. When he is born, he receives his ruach. Finally, when he begins to nurse, he receives a neshamah.

Not everyone receives a chayah, he says. Upon a person reaching maturity, repeatedly performing mitzvot and allowing one’s good inclination to guide oneself readies one to receive a chayah. As far as the yechidah is concerned, only Moshe was able to receive it during his lifetime. He notes that the perfectly righteous are able to receive a yechidah after their deaths.

Rabbi Yitzchak Karo (1458-1535) – an uncle of the more famous Rabbi Yosef Karo – writes that if one views the five words for the soul as powering different parts of the body, we get: The neshamah powers one’s head and brain (nervous system), the chayah powers one’s respiratory system, the yechidah powers one’s hands (which make man unique amongst the animal kingdom), the ruach powers the heart (circulatory system), and the nefesh powers the legs (ambulatory system).

Rabbi Karo also cites a tradition that the names for the soul correspond to five different stages of life. When a baby is first born, his soul is called neshamah because that’s when he first begins to breathe. When he turns 10, his soul is called ruach because he is now imbued with a yetzer tov that helps him fight off his yetzer hara. When he turns 20, the battle between the yetzer tov and yetzer hara calms down a bit such that his soul is now called nefesh, which is an expression of rest or respite.

From 30 until 40, a soul is called a chayah because the person can be assumed to have performed so many mitzvot that the merits he attained from them serve as the basis of his life-force. By 40, a person yetzer hara can be almost completely subdued, so that from that age until a person’s demise, his soul is called a yechidah as his yetzer tov is there alone without the yetzer hara thwarting its efforts.

(After citing this tradition, Rabbi Karo offers a slightly modified version of it, dividing the five time-periods as spanning from birth to 13, from 13 to 25, from 25 to 40, from 40 to 60, and from 60 until death. Special thanks to Dr. Shaul Regev for sending me the relevant sources from his edition of Rabbi Karo’s homilies.)

Rabbi Reuven Chaim Klein is the author of “Lashon HaKodesh” and the recently-published “G-d Versus Gods: Judaism in the Age of Idolatry.” He currently lives with his family in Beitar Illit, Israel and can be reached at [email protected]. A form of this column also appears on Ohr Somayach’s website.

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Rabbi Reuven Chaim Klein writes The Jewish Press's "Fascinating Explorations in Lashon Hakodesh" column.