Explainer
A canteen is a portable water container for hikers and soldiers, and its cup boils water and cooks meals. See its uses, other meanings and what the cup adds.
The word canteen names a water bottle, a workplace cafeteria, a soldiers' bar and a box of cutlery, and only one of those matters at a campfire. For hikers, campers and anyone building an emergency kit, a canteen is a sturdy bottle that carries water and, in its single-wall steel form, can also heat it.
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In the outdoors, a canteen is a small container for carrying water or another drink, long associated with soldiers and travellers. A modern one is usually a wide-mouth bottle with a screw cap, often sold with a cup that nests against it for carrying.
Canteen sizes and volumes start around one quart for the classic military pattern and climb from there, so the same word covers a slim hip bottle and a bottle sized for a small group.
Away from camp, the word turns up in several everyday senses, which is why searches for it return a mixed bag.
Heating water is where canteen design matters most. A single-wall stainless steel bottle with no vacuum layer can be heated over a fire or stove, which lets it purify water by boiling, make coffee or tea, or turn snow into something drinkable. Vacuum-insulated bottles are built for the opposite job, and plastic caps and straps have to come off before any heating, so follow the maker's instructions for the specific bottle.
A lid on the cup or bottle traps the heat and brings the water to a boil faster. The canteen comparison for boiling water covers the capacity and the nesting cup of each single-wall steel model.
A canteen cup is a cup that nests at the top or bottom of the canteen, and it is what turns a bottle into a small cook kit.
Canteens are still issued to members of the armed forces, but they see little use outside training. The canteen cup is used more often.
A military-style canteen cup holds about 24 ounces when filled to the brim, and outdoor sets commonly pair a bottle with a cup of roughly 24 to 25 ounces.
It most likely comes from the French cantine, meaning a bottle case or a sutler's shop, which in turn came from the Italian cantina, a wine cellar. The first known use in English dates to 1707.