Infix notation
Mathematics notation with operators between operands
Infix notation is the notation commonly used in arithmetical and logical formulae and statements. It is characterized by the placement of operators between operands—"infixed operators"—such as the plus sign in 2 + 2.
Usage
Binary relations are often denoted by an infix symbol such as set membership a ∈ A when the set A has a for an element. In geometry, perpendicular lines a and b are denoted
a
⊥
b
,
{\displaystyle a\perp b\ ,}
and in projective geometry two points b and c are in perspective when
b
⩞
c
{\displaystyle b\ \doublebarwedge \ c}
while they are connected by a projectivity when
b
⊼
c
.
{\displaystyle b\ \barwedge \ c.}
Infix notation is more difficult to parse by computers than prefix notation (e.g. + 2 2) or postfix notation (e.g. 2 2 +). However many programming languages use it due to its familiarity. It is more used in arithmetic, e.g. 5 × 6.
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