The difference between Unalterable and Variable

When used as adjectives, unalterable means incapable of changing or being altered, whereas variable means able to vary.

Variable is also noun with the meaning: something that is variable.

check bellow for the other definitions of Unalterable and Variable

Variable as an adjective:

Able to vary.

Examples:

"variable winds or seasons; a variable quantity"
Variable as an adjective:

Likely to vary.
Variable as an adjective:

Marked by diversity or difference.
Variable as an adjective (mathematics):

Having no fixed quantitative value.
Variable as an adjective (biology):

Tending to deviate from a normal or recognized type.

Variable as a noun:

Something that is variable.
Variable as a noun:

Something whose value may be dictated or discovered.

Examples:

"There are several variables to consider here."
Variable as a noun (mathematics):

A quantity that may assume any one of a set of values.
Variable as a noun (mathematics):

A symbol representing a variable.
Variable as a noun (programming):

A named memory location in which a program can store intermediate results and from which it can read them.
Variable as a noun (astronomy):

A variable star.
Variable as a noun (nautical):

A shifting wind, or one that varies in force.
Variable as a noun (nautical, in the plural):

Those parts of the sea where a steady wind is not expected, especially the parts between the trade-wind belts.