Is uttering foreign words like "Okay" and "Bye" sometimes forbidden (haram)?

It is not appropriate for a Muslim to speak in a language other than Arabic without need, if he is able to do otherwise, because the Arabic language is the emblem of Islam and its people. Languages are among the greatest emblems of nations by which they are distinguished. Al-Shafi'i disliked calling a merchant a “simsar” (broker), and that one who knows Arabic should be called a “tajir” (merchant) except if he is a merchant, and that he should speak in Arabic and then name something in a foreign language, because the language that Allah chose is the language of the Arabs, for He revealed His Book in it, and made it the language of the Seal of His Prophets. And becoming accustomed to addressing others in a language other than Arabic is disliked, because it is an imitation of the non-Arabs, and becoming accustomed to a language clearly affects the intellect, character, and religion.