When the words are foreign words and adopt the original phonetics.
Banjo comes from English, in Spanish there are both Banjo and Banyo, as it is pronounced.
Ninja comes from the Japanese and is pronounced with its original phonetics.
I didn't find any another word with "nj" from 2900 pronounced as the English "j".
But, sometimes the "j" is pronounced as in English in some words, especially anglicisms. For example:
- Jean is never pronounced j.e.a.n but as "dʒin" (Spanish pronuntiation)
- The same with Jogging, Jet, Jet set, Jet lag, Jumbo, Jazz, Junior, words all accepted in the RAE.
Sometimes it depends on the meaning or use:
Jaguar the animal is pronounced like the Spanish "j"
Jaguar the car, like the "j" in English
Ginebra is pronounced with the Spanish "g", similar to the Spanish "j" sound
Gin is pronounced with the original English phonetics
The same happens with some Gallicisms, where the
g are not (or rarely are) pronounced with the Spanish sound but with the French one:
- Beige, Collage, Déjà vu,
- Garaje, with the original phonetics in Latin America, not in Spain.
And of course all personal names: John Travolta, Michael Jackson, Norma Jean, Jean Luc Godard, Jessica Rabbit.