Pas de Calais vs Strait of Calais

Pas de Calais and Strait of Calais both are nouns.

Word	Noun	Adjective	Verb	Adverb
Pas de Calais	Yes	No	No	No
Strait of Calais	Yes	No	No	No

As nouns, Pas de Calais and Strait of Calais are synonyms defined as:

Pas de Calais and Strait of Calais: the strait between the English Channel and the North Sea; shortest distance between England and the European continent

Other synonyms of Pas de Calais include Strait of Dover.

Pas de Calais (noun)	Strait of Calais (noun)
the strait between the English Channel and the North Sea; shortest distance between England and the European continent	the strait between the English Channel and the North Sea; shortest distance between England and the European continent