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?
What does 你吃了吗？mean?
"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?"
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.
Therefore, the common meanings of this sentence are probably the two above.
What other slang words are there?
Ⅰ. The synonymous greetings of 你吃了嗎？:
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.
Ⅱ. Other greetings:
In addition to 您好, 嗨, 哈囉 and the like, some common greetings are listed below.
晚安 before bed is not a greeting phrase, of course, when we see somebody.
⒉ Relating to their action or appearance:
˙ 對孩童（To children）
˙ Going to school?
˙ 對上班族（To (office) workers）
˙ Going to work?
˙ 對主婦（To housewives）
˙ Going to the market?
˙ Going food shopping?
˙ 回家時段 (Late afternoon)
˙ Are classes over?
˙ Coming back from school?
˙ Getting off work?
˙ Coming back?
˙ Are you tired?
˙ 晚餐後 (Evening)
˙ Taking a walk?
˙ Going to the night market?
˙ 過年時 (Chinese New Year)
˙ Gōng Xĭ! Gōng Xĭ!
˙ Going to pay New Year's call?
˙ 穿著運動服 (Wearing sportswear)
˙ Going to exercise?
˙ 牽著狗 (Walking with a dog)
˙ Walking the dog?
There are many greetings like these.
Ⅲ. Other slang words:
It's too broad to answer.
Two sentences must be specified.
This is a very common sentence in Taiwan. That is, the literal meaning is extended to be a greeting.
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?
So, do not casually say this in mainland China.
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
Thus, do not say this to the Koreans.
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.
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
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.