咖啡因是一種天然興奮劑，常見於咖啡、茶和能量飲料中。
主要定義
EN: A natural stimulant found in coffee, tea, and some plants.
翻譯: 一種天然興奮劑，存在於咖啡、茶和一些植物中。
作用與效果
EN: It stimulates the central nervous system, temporarily warding off drowsiness and restoring alertness.
翻譯: 它能刺激中樞神經系統，暫時驅走睡意並恢復警覺性。
常見來源
EN: The main active ingredient in beverages like coffee, tea, cola, and energy drinks.
翻譯: 是咖啡、茶、可樂和能量飲料等飲品中的主要活性成分。
健康影響
EN: Consumed in moderation, it can enhance focus; excessive intake may cause anxiety or insomnia.
翻譯: 適量攝取可提升專注力；過量攝取可能導致焦慮或失眠。
小提醒：注意，咖啡因不僅存在於咖啡中，茶、巧克力、某些藥物和能量飲料也含有咖啡因。
點擊下方的 US / UK 按鈕可播放發音。
Real-life Examples of "Caffeine" from YouTube Videos
Gary Wolf: The quantified self
TED
“I had about 600 milligrams of caffeine, zero of alcohol And my score on the Narcissism Personality Index or the NPI-16, is a reassuring 0.31..”
1. a bitter, crystalline substance found in coffee, tea, and some sodas that stimulates the central nervous system
一種存在於咖啡、茶和一些汽水中的苦味結晶物質，能刺激中樞神經系統
Coffee contains a significant amount of caffeine.
咖啡含有大量的咖啡因。
She avoids caffeine after 3 PM to help her sleep better.
為了睡得更好，她下午三點後就避免攝取咖啡因。
2. the stimulating effect or energy boost provided by consuming caffeinated drinks
飲用含咖啡因飲料所帶來的提神效果或能量提升
I need my morning caffeine to start the day.
我需要早晨的咖啡因來開始新的一天。
The caffeine from that espresso really kicked in during the meeting.
那杯濃縮咖啡的提神效果在會議期間真的發揮作用了。
3. a common additive in some medications, energy drinks, and supplements for its stimulant properties
因其刺激特性而常見於某些藥物、能量飲料和補充劑中的添加物
Some headache pills include caffeine to enhance their effectiveness.
有些頭痛藥含有咖啡因，以增強其效果。
The pre-workout supplement is loaded with caffeine.
這種運動前補充劑含有大量咖啡因。
| Pattern | Meaning | Example |
|---|---|---|
| caffeine + noun | 咖啡因 + 名詞 | The caffeine content in this coffee is very high. (這杯咖啡的咖啡因含量很高。) |
| be + high in caffeine | 咖啡因含量高 | Energy drinks are often high in caffeine. (能量飲料通常咖啡因含量很高。) |
| be + sensitive to caffeine | 對咖啡因敏感 | I am sensitive to caffeine, so I avoid coffee after noon. (我對咖啡因很敏感，所以中午過後就不喝咖啡。) |
| cut down on caffeine | 減少咖啡因攝取 | My doctor advised me to cut down on caffeine. (我的醫生建議我減少咖啡因攝取。) |
| a dose of caffeine | 一份/一劑咖啡因 | I need a morning dose of caffeine to wake up. (我需要早晨的一份咖啡因來提神。) |
| caffeine-free | 不含咖啡因的 | She ordered a caffeine-free herbal tea. (她點了一杯不含咖啡因的草本茶。) |
| the effects of caffeine | 咖啡因的效果 | The effects of caffeine can last for several hours. (咖啡因的效果可以持續好幾個小時。) |
caffeine drink）是常見的混淆。
EN: This coffee has a high level of caffeine.
翻譯: 這杯咖啡的咖啡因含量很高。EN:I prefer caffeinated drinks in the morning.
翻譯:我早上偏好喝含咖啡因的飲料。
EN:She is trying to reduce her caffeine intake.
翻譯:她正試圖減少咖啡因的攝取量。
EN:Most sodas are caffeinated beverages.
翻譯:大多數汽水都是含咖啡因的飲料。
討論物質時用名詞 caffeine，描述產品特性時則用形容詞 caffeinated。
caffeine vs coffee
Caffeine（咖啡因）是一種化學物質，而 coffee（咖啡）是一種含有咖啡因的飲料。
caffeine vs theine
Caffeine（咖啡因）和 theine（茶鹼）在化學上是同一種物質，但傳統上因來源（咖啡豆 vs 茶葉）而有不同名稱。
caffeine vs stimulant
Caffeine（咖啡因）是 stimulant（興奮劑）的一種具體類型。
在對話中，人們常會引述自己或他人關於咖啡因的言論。 EN: I was like, "I need some caffeine to get through this meeting." 翻譯: 我那時心想：「我需要一些咖啡因才能撐過這場會議。」
EN:She told me, "Too much caffeine makes me jittery."
翻譯:她告訴我：「太多咖啡因會讓我神經緊張。」
說話者會用誇張或強調的語氣來表達對咖啡因的依賴或感受。 EN: I am so desperate for caffeine right now. 翻譯: 我現在超級渴望咖啡因的。
EN:This coffee has zero caffeine? That's literally useless to me.
翻譯:這咖啡零咖啡因？那對我來說根本沒用。
在組織思緒或短暫停頓時，可能會插入關於咖啡因的短句。 EN: My morning routine... you know, getting that caffeine fix... is sacred. 翻譯: 我的早晨慣例…你知道的，來點咖啡因…是神聖不可侵犯的。
EN:The problem is — how do I put this — my caffeine tolerance is too high now.
翻譯:問題是—我該怎麼說—我現在對咖啡因的耐受度太高了。
正式寫作注意：上述口語用法（如直接引述、誇張語氣詞、停頓填充詞）在學術論文、正式報告或商業文件中應避免使用。在正式寫作中，應使用更精確、客觀的表述，例如「咖啡因攝取」、「咖啡因的生理影響」、「對咖啡因的依賴性」等。
caffeine content
noun + noun
咖啡因含量
caffeine addict
noun + noun
咖啡因成癮者
caffeine-free
adjective
無咖啡因的
caffeine buzz
noun + noun
咖啡因帶來的興奮感
caffeine withdrawal
noun + noun
咖啡因戒斷
caffeine kick
noun + noun
咖啡因的提神效果
caffeine-induced
adjective
由咖啡因引起的
×I need a caffeine.
✓I need some caffeine.
Caffeine is an uncountable noun (like water or sugar). Do not use 'a' or 'an' before it. Use quantifiers like 'some', 'a lot of', or 'a little' instead.
×I try to avoid caffiene.
✓I try to avoid caffeine.
The correct spelling is 'caffeine', with 'ei' not 'ie'. Remember the common pattern: 'ei' after 'c' (e.g., receive, deceive).
×The caffeine is a stimulant.
✓Caffeine is a stimulant.
When talking about caffeine in general as a substance, do not use the definite article 'the'. Use the zero article.
×This coffee's caffeine is strong.
✓This coffee has a lot of caffeine.
While grammatically possible, using the possessive ('s) with substances like caffeine sounds unnatural. It's more natural to use 'has' or 'contains'.
×I consumed too many caffeines today.
✓I consumed too much caffeine today.
Caffeine is uncountable. Do not add an 's' to make it plural. Use 'much', 'a lot of', or specific measurements (e.g., milligrams of caffeine) instead.
×I am addicted to coffee because of its caffein.
✓I am addicted to coffee because of its caffeine.
The full, correct word is 'caffeine'. 'Caffein' is an outdated or scientific variant and is not used in everyday English.