As I believe "alphabet" refers specifically to the latin a-z, is there a term that collectively refers to all collections of writing characters. ie, if I had a list that contained the entries "Latin, Kanji, Cyrillic" etc, what would that list be called? A single word is preferable, as I need the term to describe such a list in software I'm writing.
Note the answer is not "language" – eg English, French, German etc are all languages, but all use the Latin alphabet. On the other hand, Japanese is a language that can be written using Kanji, Hiragana, Katakana and Latin 'systems'. It's a hypernym for these 'systems' I'm after, not the languages.
Best Answer
Alphabet is the correct word.
Your assumption is wrong.
The etymological origin of the word "alphabet" relates to the Greek alphabet, in which the first two characters are "alpha" and "beta".
However, "alphabet" is currently used for any comprehensive set of characters. Take note of definition 1.1, which shows you that it can be used more loosely and does not even need to refer to a linguistic character set.
The OED does mention that it can be taken to refer to the A-Z alphabet, but not exclusively.
Tangentially
You've somewhat answered your own question. From your question body:
If you assume that "alphabet" inherently refers to the Latin A-Z, then why didn't you say:
The fact that you have to say "the Latin alphabet" contradicts your notion that "alphabet" always refers to the Latin A-Z. That would make "Latin alphabet" a pleonasm.
Needing to specify which alphabet means that there is more than one alphabet.