Learn English – when to use Wait and when to use await

MT_Head's answer is spot on — saying "I'm full" isn't rude.

I don't think there is another single word that is similarly polite and well-understood.

If you want to avoid saying "I'm full", you could say things like, "I've had plenty," or "I've had too much already."

Host: "Would you like any more?"

Guest: "Oh, no thank you, I've had plenty. This was all wonderful, thank you."

Or...

Host: "Do you care for seconds?"

Guest: (leaning back) "Oh, no I can't, I've had too much already. Thank you, it was delicious!"

Or...

Host: "Please help yourself, there's plenty more."

Guest: "Oh, no, don't tempt me!" ( in a joking / laughing manner ) "No, I better not, thank you. This was all fantastic!"

All of these are ways to avoid saying "I'm full" which would sound natural. However, be prepared that "I'm full" is probably the keyword your host is looking for, so if they insist...

Host: "Are you sure? There's more dessert!"

Guest: "No, no I really can't. I'm perfectly satisfied right now, if I ate any more it would be too much."

In this way you can imply to your American host that you are not turning down the food because it isn't good, but because you really have eaten all you would like to eat — or even a few bites too much.

Really I think what this (sadly) reflects is that we Americans are prone to eating too much food when we really like it, so if you don't seem to have eaten "a little too much" your host may wonder if the meal wasn't to your liking.

So, while you don't have to say it yourself, it's probably best to understand that this is reason people in America say "I'm full." You're indicating to the host that the food was so irresistible you already had a little bit too much, and now you really must decline (or risk being sick!).

As an American this isn't part of my culture that I'm especially proud of, but it is what it is, and it's better to understand than to remain uncomfortable with it.

I hope this helps! Good question, by the way :)

Regarding "do the needful", Wikipedia has an article on the subject. It indicates that it was more common in English in the past. I don't think it is grammatically wrong; it is just more a matter of idiom in US/UK English. There we would more likely say "do what is necessary" or "do whatever it takes".

The same is true with pluck the flowers. It is grammatically fine; it is just not the idiom.

In regards to prepone, this is an Indian coining, and I personally think it is a great word. However, it has not made its way to Europe and the US. Frankly, I think it is our loss.

Indian English is a perfectly legitimate dialect of English and need in no way feel inferior to the mother country's version. On the contrary, India has been an abundant supplier of words and phrases to British English, and we owe the Indians a debt of gratitude in that respect. "Pluck the flowers" might be a little odd sounding to the British or American ear, but Americans "could care less", while Brits "couldn't care less", and Americans don't get too pissed, and Brits don't get too pissed off at each other about the differences.

As we English speakers like to say: vive la différence.