1. As a noun:
* An assumed name or identity: This is the most common use of "alias". Someone might use an alias to protect their identity or to avoid detection. For example, "The thief used the alias 'John Smith' to escape."
* A secondary name for a person or thing: For example, "The author's pen name, 'J.R. Smith', was an alias."
2. As a preposition:
* Meaning "otherwise known as" or "also known as": This is used to introduce an alternative name or identity. For example, "The famous artist, alias 'The Shadow', was known for his mysterious paintings."
In summary, "alias" essentially means "another name" or "a different identity."