In article , Arklin K.
wrote:

The D40, D60, and the D5000 all take AF-S lenses with the motor in the
lens. Other Nikon lenses that will fit camera body will not autofocus.
You can manually focus, though.

I'm curious.

This is great information.

But how do you know that?

it's common knowledge, and it also says that in the specs.

That is, what specific 'feature' do I look for in a lens to know if it
will work with my existing D40/D60/D5000 Nikons and how it will work in a
'future' unspecified as yet Nikon 'war camera'?

a 'war camera' is likely to have a focus motor in the body because it's
not going to be a low end model.

Is it the "AF-S" feature alone?

af-s means the lens has an internal focus motor so it doesn't matter if
there is one in the camera body.

non af-s lenses do not have an internal focus motor, which means the
camera body has to have the motor. if you use a non-afs lens on a
camera that lacks a focus motor, it will not autofocus. however, the
autofocus system is still running and you will have focus confirmation
as you manually turn the focus ring.