Formula

On the left is a sphere, whose volume V  is given by the mathematical formula V = 4/3 π r³. On the right is the compound isobutane, which has chemical formula (CH₃)₃CH.

In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a chemical formula. The informal use of the term formula in science refers to the general construct of a relationship between given quantities.

The plural of formula can be either formulas (from the most common

In mathematical logic, a formula (often referred to as a well-formed formula) is an entity constructed using the symbols and formation rules of a given logical language.^[7] For example, in first-order logic,

${\displaystyle \forall x\forall y(P(f(x))\rightarrow \neg (P(x)\rightarrow Q(f(y),x,z)))}$

is a formula, provided that ${\displaystyle f}$ is a unary function symbol, ${\displaystyle P}$ a unary predicate symbol, and ${\displaystyle Q}$ a ternary predicate symbol.

Chemical formulas

In

${\displaystyle {\ce {H-{\overset {\displaystyle H \atop |}{\underset {| \atop \displaystyle H}{C}}}-{\overset {\displaystyle H \atop |}{\underset {| \atop \displaystyle H}{C}}}-{\overset {\displaystyle H \atop |}{\underset {| \atop \displaystyle H}{C}}}-{\overset {\displaystyle H \atop |}{\underset {| \atop \displaystyle H}{C}}}-H}}}$

The structural formula for butane. There are three common non-pictorial types of chemical formulas for this molecule:

• the empirical formula C₂H₅
• the molecular formula C₄H₁₀ and
• the condensed formula (or semi-structural formula) CH₃CH₂CH₂CH₃.

A chemical formula identifies each constituent element by its chemical symbol, and indicates the proportionate number of atoms of each element.

In empirical formulas, these proportions begin with a key element and then assign numbers of atoms of the other elements in the compound—as ratios to the key element. For molecular compounds, these ratio numbers can always be expressed as whole numbers. For example, the empirical formula of ethanol may be written C₂H₆O,^[10] because the molecules of ethanol all contain two carbon atoms, six hydrogen atoms, and one oxygen atom. Some types of ionic compounds, however, cannot be written as empirical formulas which contains only the whole numbers. An example is boron carbide, whose formula of CB_n is a variable non-whole number ratio, with n ranging from over 4 to more than 6.5.

When the chemical compound of the formula consists of simple

A structural formula is a drawing that shows the location of each atom, and which atoms it binds to.

In computing

In

Degrees Celsius = (5/9)*(Degrees Fahrenheit  - 32)

In computer

=A1+A2

where A1 and A2 refer to other cells (column A, row 1 or 2) within the spreadsheet. This is a shortcut for the "paper" form A3 = A1+A2, where A3 is, by convention, omitted because the result is always stored in the cell itself, making the stating of the name redundant.

Units

Formulas used in science almost always require a choice of units.^[11] Formulas are used to express relationships between various quantities, such as temperature, mass, or charge in physics; supply, profit, or demand in economics; or a wide range of other quantities in other disciplines.

An example of a formula used in science is

${\displaystyle S=k\cdot \log W}$           (1) S= k ln W

where k is

See also

• Formula editor
• Formula unit
• Mathematical notation
• Scientific law
• Symbol (chemical element)
• Theorem
• Well-formed formula

References