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  2. Relative density - Wikipedia

    en.wikipedia.org/wiki/Relative_density

    A United States Navy Aviation boatswain's mate tests the specific gravity of JP-5 fuel. Relative density, also called specific gravity, [1] [2] is a dimensionless quantity defined as the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material.

  3. Avogadro constant - Wikipedia

    en.wikipedia.org/wiki/Avogadro_constant

    By this old definition, the numerical value of the Avogadro constant in mol −1 (the Avogadro number) was a physical constant that had to be determined experimentally. The redefinition of the mole in 2019, as being the amount of substance containing exactly 6.022 140 76 × 10 23 particles, [ 9 ] meant that the mass of 1 mole of a substance is ...

  4. Mathematics - Wikipedia

    en.wikipedia.org/wiki/Mathematics

    Aristotle defined mathematics as "the science of quantity" and this definition prevailed until the 18th century. However, Aristotle also noted a focus on quantity alone may not distinguish mathematics from sciences like physics; in his view, abstraction and studying quantity as a property "separable in thought" from real instances set ...

  5. Science - Wikipedia

    en.wikipedia.org/wiki/Science

    Science is a systematic discipline that builds and organises knowledge in the form of testable hypotheses and predictions about the universe. [1] [2] Modern science is typically divided into two or three major branches: [3] the natural sciences (e.g., physics, chemistry, and biology), which study the physical world; and the social sciences (e.g., economics, psychology, and sociology), which ...

  6. Pi - Wikipedia

    en.wikipedia.org/wiki/Pi

    The number π (/ p aɪ / ⓘ; spelled out as "pi") is a mathematical constant, approximately equal to 3.14159, that is the ratio of a circle's circumference to its diameter.It appears in many formulae across mathematics and physics, and some of these formulae are commonly used for defining π, to avoid relying on the definition of the length of a curve.

  7. Algebra - Wikipedia

    en.wikipedia.org/wiki/Algebra

    Algebra is the branch of mathematics that studies certain abstract systems, known as algebraic structures, and the manipulation of expressions within those systems. It is a generalization of arithmetic that introduces variables and algebraic operations other than the standard arithmetic operations, such as addition and multiplication.

  8. Logarithm - Wikipedia

    en.wikipedia.org/wiki/Logarithm

    In mathematics, the logarithm of a number is the exponent by which another fixed value, the base, must be raised to produce that number.For example, the logarithm of 1000 to base 10 is 3, because 1000 is 10 to the 3 rd power: 1000 = 10 3 = 10 × 10 × 10.

  9. pH - Wikipedia

    en.wikipedia.org/wiki/PH

    This was the original definition of Sørensen in 1909, [18] which was superseded in favor of pH in 1924. [H] is the concentration of hydrogen ions, denoted [ H + ] in modern chemistry. More correctly, the thermodynamic activity of H + in dilute solution should be replaced by [ H + ]/ c 0 , where the standard state concentration c 0 = 1 mol/L.