Check that wireless thing in your purse or pocket. Is it a computer or a phone?
Today the odds are heavily in favour of it being a phone, but there's no guarantee that it will be tomorrow.
And with telephone traffic changing from voice to data - to web pages, instant messages, music files, and games - the computer industry is keen to get in on the action .
In his keynote speech at Comdex, Jorma Ollila, chairman and chief executive officer of Nokia Corporation, was suitably triumphalist.
The mobile phone is "the world's fastest growing and most global consumer electronics device", he said.
"There are now more mobile phones in use than wired lines, and in the next six months, the number will go beyond 1bn."
At the same time, Mr Ollila announced that Nokia would start licensing some of its core software technologies to rivals.
Korea's Samsung Electronics has been the first to sign up. And in another Comdex announcement, Nokia and Sony agreed to work together to enable devices to exchange data and content.
"This is a task which requires broad and open interoperability between devices from many manufacturers," said Mr Ollila.
Nokia, as the dominant handset supplier, clearly wants to get its software accepted as the standard.
If it fails, it could eventually find itself marooned and overwhelmed, like Apple in the personal computer market.
So far, mobile phone manufacturers have done well in the voice business, and thanks to the GSM standard, most mobile users can talk to most other mobile users.
That is not always the case with data, apart from SMS text messages, which will not be around much longer in any case.
Data standards for things like contact and calendar data, instant messages, electronic mail and web pages are, by and large, being established in the computer industry.
The computer industry is making a hash of it, as usual, but it is still a long way ahead of the mobile phone industry.
And if the mobile phone companies lose control of their software standards, it could be very hard for them to hang on to the hardware business.
Indeed, most "smart phones" are already based on software developed for handheld computers.
The main suppliers are Symbian (using software developed originally for Psion handhelds), Microsoft (with a version of its PocketPC software), and Palm, which licences Palm OS.
The problem is that adding applications and data support involves a lot of work for phone manufacturers, whereas adding GSM telephony is relatively easy for computer manufacturers.
One of the first challengers from the computer side of the business is the Handspring Treo, which should be on sale in the US before Christmas.
Jeff Hawkins, founder and chairman of Handspring, devoted much of his Comdex speech on Tuesday to demonstrating the device, which combines the facilities of a Palm personal organiser, a RIM Blackberry and a pager with a mobile phone.
The result is much smaller, and much cheaper, than Nokia's Communicator.
Afterwards, Mr Hawkins said he was not afraid of competing against big companies such as Nokia, and he was sceptical of the various cooperative deals announced during Comdex.
"It's very easy to say this sort of thing; it's very difficult to pull it off," he said. "You don't create great products by announcing initiatives."
