It’s called “formula”, not “function”.

Thanks for the correction. Do I not get the choice because I am using the free version and am only a collaborator?

What is the exact problem you’re having? Posting screenshots or a video would be helpful.

I am unable to get fxformula as a choice in field type selection menu.

For some reason, formula fields can’t be created nor edited in the mobile app. You may want to submit this as a feature request to support@airtable.com.

Awesome, been driving me crazy. Thanks

It’s definitely an odd omission — it would be very nice to be able to create formula fields from the iPad or the iPhone. You can “sort of do it” from an iPad web browser window, but it’s difficult.