[MMM]

Thank you, Nyororin for distinguishing "romaji" and the "English alphabet".

Indeed, romaji is the use of the English alphabet to write words in Japanese.

パン　is "pan" in romaji and "bread" in English.

And yes, it would be a mistake to say that hiragana, katakana, romaji and kanji are "interchangeble".

A word like 喫茶店　(tea room) CAN be written using all four systems, but I have certainly almost never seen the word written in romaji and have never seen it written in katakana. I can only ever seeing it written in hiragana in textbooks, but 99% of the time you will see it in kanji.

I don't beleive I said they are "interchangeable", which they aren't, but they they are used in conjunction with each other. (EDIT: Now I see it was Killrb that said that.) The pic I included was one case. They sentence I described was another (and we are mixing talking about "sentences" and "just usage" like in street signs. The use of the English alphabet is much more common on street signs, shop windows, advertisements, etc. than it is in novels, news stories, contracts, etc.).

But, as I said, the Japanese are very familiar with the English alphabet, and are not intimidated by its use.

Which leads me to a question. Abbreviations, like "KY" (short for 空気を読めない, Kuuki wo Yomeni, or someone who has difficulty reading a situation). Is "KY" romaji? English?