**There are multiple versions of the multiplication sign.**

**
Classic Multiplication Sign
**Sign: ×

3 × 5 = 15

Alternative Multiplication Signs

In order to avoid confusion between the classic multiplication sign × and the letter x (often used in algebra), alternative multiplication signs were invented.

Sign: ·

3 · 5 = 15

Sign: *

3 * 5 = 15

Invisible Multiplication Signs

When a number is immediately adjacent to a letter or parenthesis, an invisible multiplication sign is in force.

3a = 3 × a

3(a) = 3 × a

3(5) = 3 × 5

When a number is immediately adjacent to an operation in parenthesis, an invisible multiplication sign is in force.

2(a + 4) = 2 × a + 2 × 4

2(a – 4) = 2 × a – 2 × 4

When a letter is immediately adjacent to a number, letter, or parenthesis, an invisible multiplication sign is in force.

a3 = a × 3

ab = a × b

a(3) = a × 3

a(b) = a × b

When a letter is immediately adjacent to an operation in parenthesis, an invisible multiplication sign is in force.

a(b + 4) = a × b + a × 4

a(b – 4) = a × b – a × 4

When π is immediately adjacent to a number, letter or parenthesis, an invisible multiplication sign is in force.

3π= 3 × π

aπ = a × π

π(3) = π × 3

π(a) = π × a

When the root sign √ is immediately adjacent to a number or letter, an invisible multiplication sign is in force.

5√3 = 5 × √3

a√3 = a × √3