Rigour vs Constraint - What's the difference?

As nouns the difference between rigour and constraint

is that rigour is severity or strictness while constraint is something that constrains.

(wikipedia rigour)

* rigor (US)

(en noun)

Severity or strictness.

A trembling or shivering response.

Character of being unyielding or inflexible.

Shrewd questioning.

Higher level of difficulty.

(British, slang) An abbreviated form of rigour mortis.

* *

(wikipedia constraint)

(en noun)

Something that constrains.

(mathematics) A condition that a solution to an optimization problem must satisfy.

A restriction.

* constraint satisfaction