As a proper noun, "Watch" refers to a specific watch brand or company, such as the Swiss watchmaker "Rolex" or the Japanese electronics company "Seiko." In this case, "Watch" is capitalized because it is a proper noun representing a specific entity.
As a common noun, "watch" refers to the general concept or object of a timepiece worn on the wrist. In this sense, "watch" is not capitalized and is used in a generic manner, without referring to a particular brand or company. For example, "I need to get my watch repaired" or "I forgot my watch at home."
In some cases, the context can determine whether "watch" is used as a proper noun or a common noun. For instance, if someone mentions "the Watch," it could refer to a specific brand or type of watch, such as the Apple Watch, making it a proper noun. On the other hand, if someone says, "I need to buy a new watch," they are likely referring to a general timepiece, making "watch" a common noun.
Therefore, the classification of "watch" as a proper noun or common noun depends on its context and specific usage in a sentence.