QUAN'TITY, n. [L. quantitas, from quantus, how much, or as much as.]

1. That property of any thing which may be increased or diminished. – Cheyne. Johnson. This definition is defective, and as applicable to many other properties as to quantity. A definition strictly philosophical can not be given. In common usage, quantity is a mass or collection of matter of indeterminate dimensions, but consisting of particles which can not be distinguished, or which are not customarily distinguished, or which are considered in the aggregate. Thus we say, a quantity of earth, a quantity of water, a quantity of air, of light, of heat, of iron, of wood, of timber, of corn, of paper. But we do not say, a quantity of men, or of horses, or of houses; for as these are considered as separate individuals or beings, we call an assemblage of them, a number or multitude.
2. An indefinite extent of space.
3. A portion or part. If I were sawed into quantities. [Not in use.] – Shak.
4. A large portion; as, a medicine taken in quantities, that is, in large quantities. – Arbuthnot.
5. In mathematics, any thing which can be multiplied, divided or measured. – Day. Thus mathematics is called the science of quantity. In algebra, quantities are known and unknown. Known quantities are usually represented by the first letters of the alphabet, as a, b, c, and unknown quantities are expressed by the last letters, x, y, z, &c. Letters thus used to represent quantities are themselves called quantities. A simple quantity is expressed by one term, as +a, or -abc; a compound is expressed by more terms than one, connected by the signs, + plus, or - minus, as a + b, or a - b + c. Quantities which have the sign + prefixed, are called positive or affirmative; those which have the sign - prefixed, are called negative. – Day's Algebra.
6. In grammar, the measure of a syllable; that which determines the time in which it is pronounced. – Holder. Encyc.
7. In logic, a category, universal, or predicament; a general conception. – Bailey. Encyc.
8. In music, the relative duration of a note or syllable. – Busby. Quantity of matter, in a body, is the measure arising from the joint consideration of its magnitude and density. – Bailey. Quantity of motion, in a body, is the measure arising from the joint consideration of its quantity of matter and its velocity. – Bailey.

1. The attribute of being so much, and not more or less; the property of being measurable, or capable of increase and decrease, multiplication and division; greatness; and more concretely, that which answers the question "How much?"; measure in regard to bulk or amount; determinate or comparative dimensions; measure; amount; bulk; extent; size.
   
   
   Hence, in specific uses: (a) (Logic)
2. That which can be increased, diminished, or measured; especially (Math.), anything to which mathematical processes are applicable.
   
   

   * Quantity is discrete when it is applied to separate objects, as in number; continuous, when the parts are connected, either in succession, as in time, motion, etc., or in extension, as by the dimensions of space, viz., length, breadth, and thickness.

3. A determinate or estimated amount; a sum or bulk; a certain portion or part; sometimes, a considerable amount; a large portion, bulk, or sum; as, a medicine taken in quantities, that is, in large quantities.
   
   

   The quantity of extensive and curious information which he had picked up during many months of desultory, but not unprofitable, study. Macaulay.

   Quantity of estate (Law), its time of continuance, or degree of interest, as in fee, for life, or for years. Wharton (Law Dict. ) -- Quantity of matter, in a body, its mass, as determined by its weight, or by its momentum under a given velocity. -- Quantity of motion (Mech.), in a body, the relative amount of its motion, as measured by its momentum, varying as the product of mass and velocity. -- Known quantities (Math.), quantities whose values are given. -- Unknown quantities (Math.), quantities whose values are sought.