C# : Is Variance (Covariance / Contravariance) another word for Polymorphism?

Question

I am trying to figure out the exact meaning of the words Covariance and Contravariance from several articles online and questions on StackOverflow,

Answer 1

I found this collection:

Covariance and Contravariance in C#, Part One

Covariance and Contravariance in C#, Part Two: Array Covariance

Covariance and Contravariance in C#, Part Three: Member Group Conversion Variance

Covariance and Contravariance in C#, Part Four: Real Delegate Variance

Covariance and Contravariance In C#, Part Five: Higher Order Functions Hurt My Brain

Covariance and Contravariance in C#, Part Six: Interface Variance

Covariance and Contravariance in C# Part Seven: Why Do We Need A Syntax At All?

Covariance and Contravariance in C#, Part Eight: Syntax Options

Covariance and Contravariance in C#, Part Nine: Breaking Changes

Covariance and Contravariance in C#, Part Ten: Dealing With Ambiguity

Covariance and Contravariance, Part Eleven: To infinity, but not beyond