1. variability attributable to individual differences;

The Collaborative International Dictionary of English v.0.48:

Personal \Per"son*al\ (p[~e]r"s[u^]n*al), a. [L. personalis: cf. F. personnel.] 1. Pertaining to human beings as distinct from things. [1913 Webster] Every man so termed by way of personal difference. --Hooker. [1913 Webster] 2. Of or pertaining to a particular person; relating to, or affecting, an individual, or each of many individuals; peculiar or proper to private concerns; not public or general; as, personal comfort; personal desire. [1913 Webster] The words are conditional, -- If thou doest well, -- and so personal to Cain. --Locke. [1913 Webster] 3. Pertaining to the external or bodily appearance; corporeal; as, personal charms. --Addison. [1913 Webster] 4. Done in person; without the intervention of another. "Personal communication." --Fabyan. [1913 Webster] The immediate and personal speaking of God. --White. [1913 Webster] 5. Relating to an individual, his character, conduct, motives, or private affairs, in an invidious and offensive manner; as, personal reflections or remarks. [1913 Webster] 6. (Gram.) Denoting person; as, a personal pronoun. [1913 Webster] Personal action (Law), a suit or action by which a man claims a debt or personal duty, or damages in lieu of it; or wherein he claims satisfaction in damages for an injury to his person or property, or the specific recovery of goods or chattels; -- opposed to real action. Personal equation. (Astron.) See under Equation. Personal estate or Personal property (Law), movables; chattels; -- opposed to real estate or real property. It usually consists of things temporary and movable, including all subjects of property not of a freehold nature. Personal identity (Metaph.), the persistent and continuous unity of the individual person, which is attested by consciousness. Personal pronoun (Gram.), one of the pronouns I, thou, he, she, it, and their plurals. Personal representatives (Law), the executors or administrators of a person deceased. Personal rights, rights appertaining to the person; as, the rights of a personal security, personal liberty, and private property. Personal tithes. See under Tithe. Personal verb (Gram.), a verb which is modified or inflected to correspond with the three persons. [1913 Webster]The Collaborative International Dictionary of English v.0.48:

Equation \E*qua"tion\, n. [L. aequatio an equalizing: cf. F. ['e]quation equation. See Equate.] 1. A making equal; equal division; equality; equilibrium. [1913 Webster] Again the golden day resumed its right, And ruled in just equation with the night. --Rowe. [1913 Webster] 2. (Math.) An expression of the condition of equality between two algebraic quantities or sets of quantities, the sign = being placed between them; as, a binomial equation; a quadratic equation; an algebraic equation; a transcendental equation; an exponential equation; a logarithmic equation; a differential equation, etc. [1913 Webster] 3. (Astron.) A quantity to be applied in computing the mean place or other element of a celestial body; that is, any one of the several quantities to be added to, or taken from, its position as calculated on the hypothesis of a mean uniform motion, in order to find its true position as resulting from its actual and unequal motion. [1913 Webster] Absolute equation. See under Absolute. Equation box, or Equational box, a system of differential gearing used in spinning machines for regulating the twist of the yarn. It resembles gearing used in equation clocks for showing apparent time. Equation of the center (Astron.), the difference between the place of a planet as supposed to move uniformly in a circle, and its place as moving in an ellipse. Equations of condition (Math.), equations formed for deducing the true values of certain quantities from others on which they depend, when different sets of the latter, as given by observation, would yield different values of the quantities sought, and the number of equations that may be found is greater than the number of unknown quantities. Equation of a curve (Math.), an equation which expresses the relation between the co["o]rdinates of every point in the curve. Equation of equinoxes (Astron.), the difference between the mean and apparent places of the equinox. Equation of payments (Arith.), the process of finding the mean time of payment of several sums due at different times. Equation of time (Astron.), the difference between mean and apparent time, or between the time of day indicated by the sun, and that by a perfect clock going uniformly all the year round. Equation clock or Equation watch, a timepiece made to exhibit the differences between mean solar and apparent solar time. --Knight. Normal equation. See under Normal. Personal equation (Astron.), the difference between an observed result and the true qualities or peculiarities in the observer; particularly the difference, in an average of a large number of observation, between the instant when an observer notes a phenomenon, as the transit of a star, and the assumed instant of its actual occurrence; or, relatively, the difference between these instants as noted by two observers. It is usually only a fraction of a second; -- sometimes applied loosely to differences of judgment or method occasioned by temperamental qualities of individuals. Theory of equations (Math.), the branch of algebra that treats of the properties of a single algebraic equation of any degree containing one unknown quantity. [1913 Webster]WordNet (r) 3.0 (2006):

personal equation n 1: variability attributable to individual differences