So there is no exact definition for a flashlight on the internet other than being a portable artificial light source with a battery inside.
What's your opinion?
Is there a certain head diameter or length or weight that will make you say "this isn't a flahslight"?
Does it need to be held in one hand?
Does it need to look like a flashlight?
Discuss below :)
I would say that any light that isn’t powered by electrical mains or a generator/alternator (or doesn’t run on an external battery that is recharged by those sources during normal operation) and isn’t primarily used on a fixed mount could be called a flashlight.
I think the definition is intentionally ambiguous so that even the really odd ones have a definition.
I would say that for my personal definition it has to be able to be carried by hand by one person. This doesn’t include headlamps as flashlights which many people might disagree with, and I’m actually unsure as to whether or not I think of a headlamp as a flashlight, but it’s a simple way of excluding backpack mounted monstrosities whether the exist or not.
As for your more specific questions, I don’t think there is a specific size or weight limit, it doesn’t have to be held in one hand, and it definitely does not have to look like a flashlight.
Thanks for giving me something interesting to think about.
When you can’t sleep at night so you grab your Reylight TI and just stare at the trits until you fall asleep and then you wake when it hits the floor.
When it stops working 
HAH good one
When the battery is depleted or absent.
(i.e. when it stops working)
But i think it should have an internal power source for it to be a flashlight.
It should also be portable.
If you have to plug it into something to work, I don’t think it’s a flashlight anymore. And yes, needs to be portable.
So how about a headlamp with a battery pack on the back of your head?
Or is it one thing because it’s fitted on a headband strap thing?
I don’t think “one handed” is enough to call something a flashlight. For example, Rayovac has a spotlight, beam lantern, and a 3D lantern. Each of these is used with one hand, but you wouldn’t think of them as “flashlights”.
I think of a “flashlight” as something that’s long shaped that you wrap your hand around and point the light beam at.
This.
When everyone refers to it as a torch!
:face_with_monocle: 
That there is another point in my view.
I think only the lantern, the 3rd link is not a flashlight.
It’s non directional light, so it’s a lantern, not a flashlight.
The other ones are flashlights in my opinion.
The fact that they have a handle in stead of a battery compartment to hold it by doesn’t make them something else.
I agree on the pointing part, but a ‘general direction’ will also do.
RAMBO…JOHN J. Been on Cable all this past week. Gotta luv it !
First Blood wasn’t a bad movie actually. 
Personally, I wouldn’t use a headlamp with a spare battery pack as a flashlight. I think that is specifically a headlamp. For me, this also applies to a light that has an internal power supply but is dedicated as a headlamp. like the Nitecore NU20. That being said, I think a light like the Skilhunt H03 fits both classifications (headlamp and flashlight) because it is designed to be used both ways.
That being said, I wouldn’t be offended if someone called an Olight H35 a flashlight. To me, it isn’t that big a deal. Potato, Potahto…A rose by any other name would smell as sweet. If you have it and I need it to provide me with light in the dark, I’ll call it whatever you want me to. 
Ah, but if you install a lantern reflector into a lantern so that the light only comes out on one side, do you call that a flashlight?
I guess it would be then, just in a weird shape 
I say any flashlight not approved by BLF is no flashlight at all …it’s just junk …
and a flashlight stops being a flashlight when you chock your rear wheel or use it to beat someone senseless .
