The difference between Impenetrable and Impregnable

When used as adjectives, impenetrable means not penetrable, whereas impregnable means too strong to be penetrated.

check bellow for the other definitions of Impenetrable and Impregnable

Impenetrable as an adjective:

Not penetrable.

Examples:

"The fortress is impenetrable, so it cannot be taken."
Impenetrable as an adjective (figuratively):

Incomprehensible; fathomless; inscrutable.

Examples:

"Business jargon makes this document impenetrable, I can't understand it."
Impenetrable as an adjective:

Opaque; obscure; not translucent or transparent.

Examples:

"When night falls, she cloaks the world in impenetrable darkness."

Impregnable as an adjective (of a fortress, wall, etc., also used figuratively):

Too strong to be penetrated.