杯（はい、hai）
- ~cups/glasses

The Japanese word 杯 (はい) is a counter word, primarily used to quantify or count the number of drinks or the contents of a cup, glass, or similar container. It indicates "a cup of," "a glass of," or a similar unit of measure. It’s also used in some contexts to refer to the container itself.

⚫︎ビールを一杯ください。 Translation: Please give me a glass of beer. ⚫︎水を二杯飲みました。 Translation: I drank two cups of water. ⚫︎お酒を三杯いただきました。 Translation: I had three glasses of alcohol.

This counter is mainly used when ordering or referring to drinks like beer, water, sake, or juice. It is important to remember to use the correct counter when counting objects in Japanese. The specific context determines the nuance - a 杯 of coffee usually indicates a cup, while a 杯 of sake usually indicates a small serving. The number precedes 杯 in the sentence. For example, 一杯 (いっぱ［い］) means "one cup/glass," 二杯 (に［はい］) means "two cups/glasses," and so on.

杯 is written with the kanji 杯. The reading is はい in hiragana. There are no other ways to write this word. Okurigana (the suffix hiragana) is not applicable here.

There are other counter words depending on the type of container or drink, but there isn’t a direct synonym that covers all of the uses of 杯: ⚫︎コップ (こっぷ): cup, glass (can be used in some situations, but not as a counter word) ⚫︎缶 (かん): can ⚫︎本 (ほん): used for long cylindrical objects (i.e. bottles of sake).

杯 itself isn’t used in a way that has a direct antonym. However, when considering the act of drinking or consuming the contents of a cup, words like: ⚫︎残す (のこす): to leave (some of a drink) ⚫︎捨てる (すてる): to throw away (the empty cup, for example).

コーヒーを一杯お願いします。 ・Translation: I would like a cup of coffee, please. ・Explanation: This sentence uses 一杯 to request a cup of coffee. The number (one) and the counter 杯 are combined to indicate the quantity.

彼女はジュースを三杯飲んだ。 ・Translation: She drank three glasses of juice. ・Explanation: This sentence uses 三杯 to show that she drank three glasses of juice. The verb 飲んだ (drank) indicates the action.

The etymology of 杯, meaning "cup" or "goblet," traces back to ancient Chinese, where 杯 originally referred to a drinking vessel made of clay or similar material. Its usage as a counter word developed over time to specify the quantity of liquids or the contents held within such vessels, and has been standardized to its current usage in Modern Japanese.