The phrase "a constant quantity" is correct and usable in written English.
It can be used in mathematical, scientific, or technical contexts to refer to a value that does not change.
Example: "In this equation, the speed of light is considered a constant quantity."
Alternatives: "an unchanging value" or "a fixed amount."
I do not believe that the tears of the world are a constant quantity.
Youthful aggression has always been a problem and always will be; the pitilessness of childhood, like that of the world, is most likely a constant quantity.
The implication is that although we cannot eliminate grief and sadness, the tears of the world are not a constant quantity – they are, instead, at least in part, a matter of choice.
This law expresses the inverse relationship that exists between the pressure and volume of a gas, and it was determined by measuring the volume occupied by a constant quantity of air when compressed by differing weights of mercury.
When we learn that household incomes have fallen for the first time in a generation, that radiation levels are rising in the seas off Japan and that regimes in the Middle East are again cracking down, with a vengeance, on their own people, it is easy to see why Samuel Beckett once wrote that the tears of the world are a constant quantity.
Each of these parameters can be defined either as a random variable or as a constant quantity.
It does not matter whether that process transmits the quantity or not, nor whether the object keeps a constant amount of the quantity.
Viète introduced the concept of algebraic variable, which he denoted using a capital vowel (A, E, I, O, U), as well as the concept of parameter (an unspecified constant quantity), denoted by a capital consonant (B, C, D, and so on).
Volume contraction causes a rise in plasma bicarbonate concentration because there is contraction of the extracellular volume around a relatively constant quantity of extracellular bicarbonate [ 8].
ABHR foams were dispensed from pumps delivering a known constant quantity (0.4 mL), and total volumes were controlled by the number of pump activations.
In a given solvent, however, the concentration of the solvent, [SH], is a large and constant quantity, and it is therefore usual to eliminate this term and express the self-dissociation of the solvent by the equation Ks = [SH2+][S−].
