* Letter Opener: This is the most straightforward and common name.
* Paper Knife: This term is more general, but it's also widely used.
* Envelope Knife: This name emphasizes its primary use.
* Letter Knife: Similar to "Envelope Knife", this emphasizes its primary function.
* Mail Opener: This name is a bit more specific to its use with mail.
You may also find other more specific names based on the design of the letter opener, such as:
* Dagger Letter Opener: A letter opener that resembles a dagger.
* Claw Letter Opener: A letter opener with a claw-like tip.
* Decorative Letter Opener: A letter opener that is also a decorative piece.
Ultimately, the "proper" name is the one that is most commonly used or understood in your context.