How do proper nouns become common nouns?

Answer 1

Proper nouns refer to very unique persons, places, or things. "The Chair" often refers to the Chairman, or sometimes also the electric chair. "The Garden" might refer to the Garden of Eden. Common nouns refer to common instances of persons, places, or things.

Proper Noun (usually capitalized) = "a specific person" (Mr. Perkins), "a specific place" (Washington DC, Mexico City), "a specific thing" (Titanic)

Common Noun = "a person" (he/she), "a place" (garden, park), or "a thing" (table, chair)

That's a bit confusing (above)

They are born common nouns - they are always common nouns. They are the words for a kind of person, thing, substance etc.

eg table, oil, friend, policeman

common nouns start with a small letter but proper nouns start with a capital letter.

Proper nouns are the names of:

places - Rome, Sri Lanka

people - Mary Mr Williams, Rupert

organizations - Microsoft, Fontera, UNESCO

Proper nouns usually refer to just one person/place/organization

Answer 2

Proper nouns become common nouns when they are used generically to refer to a specific thing or concept rather than a particular individual or entity. For example, "Kleenex" (a proper noun) has become a common noun for facial tissue. This shift can occur when a brand name becomes widely recognized and synonymous with a product or service.