The name “mastiff” can be confusing, because there are several dog breeds with that word in their names, e.g. the Neopolitan mastiff and the Tibetan mastiff. Officially, these breeds are known as “mastiff-type dogs.” When kennel clubs use the name “mastiff” without qualification, it’s usually safe to assume they’re referring to the breed also called the English mastiff or the Old English mastiff.

Reference

Ciampanelli, P. (2015) 10 Cool Facts About English Mastiffs. Retrieved from http://mom.me/pets/dogs/19368-cool-facts-about-english-mastiffs/item/english-mastiff-dressed-/