Is it "extension" or "dial string"

I keep getting the question "What is the extension?" or "What is your dial string?"

On the invite below, you use the term "extension".

Join Sales Pipeline Review on Lifesize Cloud

View dialing options or install the app:

  http://lifesizecloud.com/1289759

Join as an audio only caller:

    US: +1-844-572-5683 extension 1289759

    One Tap Dial: +18445725683,,,,1289759#

    International numbers: https://manage.lifesizecloud.com/#/numbers

When you sign in as a guest user after downloading the app, you use the term "dial string"

This message needs to be consistent. Use "extension" or "dial string" or "personal ID number" or "meeting ID" or "ID Number" or a new term - but keep it consistent please.

Also, it would make sense on the email invite to say briefly: "If instructed, please use extension: 1289759" - for example:

Join Sales Pipeline Review on Lifesize Cloud

View dialing options or install the app:

  http://lifesizecloud.com/1289759

   If instructed, use this extension: 1289759

Join as an audio only caller:

    US: +1-844-572-5683 extension 1289759

    One Tap Dial: +18445725683,,,,1289759#

    International numbers: https://manage.lifesizecloud.com/#/numbers

Thanks,

Ryan