Earl is a coordinate term of viscount.

As nouns the difference between viscount and earl

is that viscount is a member of the peerage above a baron but below a count or earl while earl is a British nobleman next in rank above a viscount and below a marquess; equivalent to a European count. A female using the style is termed a countess.

As proper nouns the difference between viscount and earl

is that viscount is a village in Saskatchewan, Canada while Earl is the title of an earl.