TCL unveils a tri-fold smart device design concept

[HEXUS]

This is a Z-fold design which transforms from a 6.65-inch phone into 10-inch tablet.

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[Giraffe]

It's actually bi-fold - there are only 2 folds in it. If I fold a sheet of paper in half it's not bi-fold - it simply has 1 fold.
Also, marketeers using mAh! Precision over accuracy by an order of magnitude - 1000xm+1.

[Ttaskmaster]

Debatably overkill, but only until these things start getting thinner.

[sinhaomar]

One more fold is worse then ever. Twice of the possibility to break it,i guess!)

[globalwarning]

It's actually bi-fold - there are only 2 folds in it. If I fold a sheet of paper in half it's not bi-fold - it simply has 1 fold.
Also, marketeers using mAh! Precision over accuracy by an order of magnitude - 1000xm+1.

Just like with wallets, they are referring to the number of sections, not the number of folds. Wallets (or doors, for example) that fold into two parts are bifold, and those that have three sections are trifold.