As an adjective:
* Descriptive: It describes something as originating from or belonging to a different country or place.
* Example: "He learned a few foreign languages."
* Classifying: It can categorize something as being of a different kind.
* Example: "The store sold foreign cars."
As a noun:
* Person: It refers to a person from another country.
* Example: "The foreign was friendly and helpful."
However, when used as a noun, it is not very common and can sometimes sound a bit outdated or formal. It's more usual to use "foreigner" to refer to a person from another country.
Therefore, in most cases, "foreign" is considered an adjective.