A single word for the expression "One Thing In Common"?

Is there a single word to replace "one thing in common"? I feel it might appear more professional, to be used say in academic work.

examples:

• They've got one thing in common.
• They have one common shared foundation.
• They have one thing in common—the user experience.

Solution 1:

I finally got down to write this sentence, and it seems more complete to the context as a whole. Thanks a lot, to @rhetorician who provided me with the word: commonality .

My written sentence:

nonetheless, perhaps the commonality they all share is the elements of user experience.

This is very good indeed.