When you ask most people the difference between common nouns and proper nouns they mostly can only tell you that proper nouns start with a capital letter.
But this has problems:
- Capital letters and writing systems as a whole are recent inventions added on to language, which is ancient and naturally ocurring.
- Many if not most writing systems do not have a distinction between upper and lower case.
- Even among languages which use a dual case writing system, not all capitalize words the same way:
- German capitalizes all nouns.
- Most romance languages at least do not capitalize the names of days of the week or months or the year whereas English does.
So is there a solid cross-linguistic concept of "proper nouns" within the discipline of linguistics, and if so how is it defined? Ie what criteria would an actual linguist use to decide whether a noun is common or proper?