What does "你吃了吗?" mean?

Question

I've been looking at some questions and I found in some of the answers that 你吃了吗 was identified as slang. I would have translated it as "have you eaten?", but I'm not sure since it's slang. I'm learning Mandarin without being in China, so I haven't been able to pick up much slang. What does 你吃了吗？mean? What other slang words are there?

Answer 1

What does 你吃了吗？mean?

「你吃了嗎？」
此句的原義是確認“吃的行為”。譬如：
「吃藥時間過了。你吃了嗎？」
「這個蛋糕很好吃。你吃了嗎？」
"Have you eaten?"
The original meaning of this sentence is to confirm the action of eating. For example,
"The time to take medicine has passed. Have you taken it?"
"This cake is very delicious. Did you eat it?"

不知道什麼時候開始，它變成「打招呼」用語。原因可能就像一般人推測的那樣：民以食為天。維持生命最重要的東西就是食物。
Nobody knows when it became a greeting. The reason may be something as most people speculate: hunger breeds discontentment. (Foodstuff is all-important to the people.) The most important thing to sustain life is food.

所以，這句話常見的意思大概就上面這兩種。
Therefore, the common meanings of this sentence are probably the two above.

---

What other slang words are there?

一、和「你吃了嗎？」同義的「打招呼」用語：
Ⅰ. The synonymous greetings of 你吃了嗎？:

　　吃了嗎？
　　吃飽了嗎？
　　吃飯了嗎？
　　吃過了嗎？

　　⒈ 可以不加「你」，因為這句話的主詞很明顯。
　　⒉ 「嗎」可以改用「沒（有）」。
　　⒊ 這些似乎不是俚語，只是一般用語。
　　⒈ We can leave out 你 because the subject of this sentence is obvious.
　　⒉ We can use 沒（有）instead of 嗎.
　　⒊ These do not seem to be slang, but common words.

二、 其他的「打招呼」用語：
Ⅱ. Other greetings:

除了「您好」、「嗨」、「哈囉」之類的以外，常見的還有以下這些。
In addition to 您好, 嗨, 哈囉 and the like, some common greetings are listed below.

　　⒈ 和時間相關的：
　　⒈ Time-related:

　　　　早！
　　　　早安！
　　　　早上好！
　　　　這麼早啊？
　　　　午安！
　　　　中午好！
　　　　下午好！
　　　　晚上好！
　　　　晚安！

　　　　「晚安」用在睡覺前，當然不算是見面的「打招呼」用語。
　　　　晚安 before bed is not a greeting phrase, of course, when we see somebody.

　　⒉ 和對方動作或外觀相關的：
　　⒉ Relating to their action or appearance:

　　　　˙ 早上（Morning）

　　　　　　˙ 對孩童（To children）

　　　　　　　　˙ 去學校啊？
　　　　　　　　˙ （去）上學啊？
　　　　　　　　˙ Going to school?

　　　　　　˙ 對上班族（To (office) workers）

　　　　　　　　˙ 去工作啊？
　　　　　　　　˙ （去）上班啊？
　　　　　　　　˙ Going to work?

　　　　　　˙ 對主婦（To housewives）

　　　　　　　　˙ 去市場啊？
　　　　　　　　˙ Going to the market?
　　　　　　　　˙ （去）買菜啊？
　　　　　　　　˙ Going food shopping?

　　　　˙ 回家時段 (Late afternoon)

　　　　　　˙ 放學了啊？
　　　　　　˙ Are classes over?
　　　　　　˙ Coming back from school?
　　　　　　˙ 下班了啊？
　　　　　　˙ Getting off work?
　　　　　　˙ 回來了啊？
　　　　　　˙ Coming back?
　　　　　　˙ 累不累啊？
　　　　　　˙ Tired?
　　　　　　˙ Are you tired?

　　　　˙ 晚餐後 (Evening)

　　　　　　˙ 去散步啊？
　　　　　　˙ Taking a walk?
　　　　　　˙ 去逛夜市啊？
　　　　　　˙ Going to the night market?

　　　　˙ 過年時 (Chinese New Year)

　　　　　　˙ 恭喜！恭喜！
　　　　　　˙ Gōng Xĭ! Gōng Xĭ!
　　　　　　˙ Congratulations!
　　　　　　˙ 去拜年啊？
　　　　　　˙ Going to pay New Year's call?

　　　　˙ 穿著運動服 (Wearing sportswear)

　　　　　　˙ （要）去運動啊？
　　　　　　˙ Going to exercise?

　　　　˙ 牽著狗 (Walking with a dog)

　　　　　　˙ 遛狗啊？
　　　　　　˙ Walking the dog?

　　　　諸如此類的，非常地多。
　　　　There are many greetings like these.

三、其他俚語：
Ⅲ. Other slang words:

　　這就太廣泛了，無法回答。
　　It's too broad to answer.

---

有兩句話必需特別說明。
Two sentences must be specified.

⒈ 你吃飽了嗎？

　　在台灣，這是很常聽到的一句話。也就是字面的意思引申為「打招呼」用語。
　　This is a very common sentence in Taiwan. That is, the literal meaning is extended to be a greeting.

　　但是在大陸，則暗示「很笨」的意思。從字面上看不出來有這個意思。我猜是因為這兩句的英文發音非常相似的緣故。
　　But, it implies "stupid" in mainland China. It does not show this meaning literally. I guess it is because the pronunciations of these two sentences in English are extremely similar.

　　你吃飽了嗎？Are you full?
　　你很愚蠢嗎？Are you fool?

　　所以在大陸不要隨便說這句話。
　　So, do not casually say this in mainland China.

⒉ 吃飽了嗎？

　　此句的發音接近韓文中一句很不雅用來罵人的話。
　　The pronunciation of this sentence is close to a very indecent Korean curse.

　　吃飽了嗎 chī bǎo le ma
　　○○○○ xi paer nao ma

　　所以，不要對韓國人說這句話。
　　Thus, do not say this to the Koreans.

Answer 2

As I was told by my teacher, it likely goes back to times when people didn't always have enough food. It's a curteous way of showing interest in the other persons wellbeing as well as being a greeting or opening to a conversation.

Answer 3

It's a common way of greeting someone. The literal translation is "have you eaten?" but in reality it's closer to "how are you doing?" or something along those lines. It also takes the forms of 吃了吗？ and 吃了没有？.

Answer 4

Just means have you already eaten.

But actuallly, it just means:

你吃了吗？ How are you? 吃了， 你呢？ Fine, thank you. and you? 我也吃过了。 I'm fine too.