Translation guide
A container that keeps liquids hot or cold by using a vacuum between double walls. In Japanese, the most common term is 魔法瓶 (mahōbin), literally 'magic bottle'. Other terms exist but are less common.
To refer to a container that keeps drinks hot or cold, typically used for coffee, tea, or water.
The standard word for a vacuum flask. Literally 'magic bottle'. Used in everyday conversation.
魔法瓶に熱いコーヒーを入れた。
I put hot coffee in the vacuum flask.
この魔法瓶は保温性が高い。
This vacuum flask keeps things hot very well.
From the brand name 'Thermos'. Often used generically, like 'Thermos' in English. Common in casual contexts.
サーモスにお茶を入れて持って行く。
I put tea in a Thermos and take it with me.
Literally 'heat-retaining bottle'. Often used for modern stainless steel flasks, especially those for cold drinks as well.
保温ボトルに氷を入れたら、ずっと冷たいままだった。
When I put ice in the insulated bottle, it stayed cold the whole time.
Technical term: 'vacuum-insulated bottle'. Used in product descriptions or specifications.
この真空断熱ボトルは軽量で持ち運びに便利です。
This vacuum-insulated bottle is lightweight and convenient to carry.