Translation guide
A thermos is a vacuum-insulated container that keeps drinks hot or cold. In Japanese, the most common equivalent is 魔法瓶 (mahōbin), but other terms exist depending on context.
The general term for a thermos, used for keeping beverages at temperature.
The standard Japanese word for a thermos or vacuum flask. Literally 'magic bottle'. Used for both hot and cold drinks.
I put hot coffee in the thermos.
A common brand name (Thermos) used generically, similar to English. Often used in casual conversation.
Let's bring a thermos to the picnic.
Literally 'heat-retaining pot'. Often used for larger tabletop dispensers, but can refer to personal thermoses.
I prepared tea in the thermos.
General term for a water bottle or canteen. Not specifically vacuum-insulated, but often used for any portable drink container.
水筒 does not necessarily imply vacuum insulation; it can be a simple bottle.
A compact, often cylindrical thermos designed for one person's beverage.
A large, often pump-action thermos used for serving hot drinks to a group.
魔法瓶 specifically means a vacuum-insulated flask. 水筒 is a broader term for any portable drink container, including non-insulated bottles. If insulation is important, use 魔法瓶.
A thermos can keep hot drinks warm for a long time.
A water bottle does not necessarily have insulation.
Like in English, brand names such as サーモス (Thermos) or 象印 (Zojirushi) are often used generically. In casual speech, saying サーモス is perfectly natural.
I filled the thermos with hot water.
She always carries a thermos of green tea.
This thermos has excellent heat retention.
Children take a water bottle to school.
マイボトルを持ち歩いて、プラスチックを減らそう。
Let's carry our own bottles to reduce plastic.