I am trying to explain to my Korean friend in the best way possible, I've got a good idea but am wondering if anyone can give me their perspective on the use of bad and badly here.
I want to go to Korea so bad.
I badly need to go to the toilet.
Note: This is not formal English, but it is heavily used in my opinion and possibly more slang than true language.
You are right, "I want to go to Korea so bad" is very informal. It's more expressive than "I want to go to Korea so badly," because bad has more impact than badly. It conveys a miserable feeling.
Your other sentence, "I badly need to go to the toilet," is correct no matter how you look at it. It's about as formal as a sentence about going to the toilet can get.
I'd recommend to use badly in this case, but the discussion about this issue is still going on according to Grammarphobia:
What your question boils down to is this: Does “want” qualify as a linking verb (one that describes a state or condition, rather than an action)?
If it does, then it’s fine to say “He wanted this bad.” If not, then good English requires “He wanted this badly.”
The short answer is that there’s no short answer, because usage authorities disagree.
Many usage guides say that “want bad” is quite common in speech and informal writing, but it doesn’t belong in formal written English.
At least one guide, however, regards “want bad” as standard English.
Our advice, particularly since you’re a student being graded on grammar, is to use “want badly” in formal written English. You can use “want bad,” if you like, in other contexts.
Here’s the story. A linking verb (like “be” or “feel” or “seem”) is modified by an adjective (like “bad”) rather than an adverb (like “badly”). So, for example, it’s perfectly correct to say “I’m good” or “I feel good” or “I’m not bad” when someone asks you how you are or how you’re feeling.
We’ve written several blog items about this subject, including one in 2009.
There are 11 verbs generally considered linking verbs: “be,” “appear,” “become,” “feel,” “grow,” “look,” “remain,” “seem,” “smell,” “sound,” and “taste.”
Since “want” isn’t one of these, it should generally be modified by an adverb (as in “he wants it greatly”) rather than an adjective (“he wants it great”).
However, “bad” is a special case and sometimes acts as an adverb, according to Merriam-Webster’s Dictionary of English Usage.
For instance, the dictionary says, “bad” is interchangeable with “badly” after the verbs “want” and “need.” So, in M-W’s opinion, expressions like “he needed it bad” and “he wanted it bad” are standard English. This makes some sense to us, since wanting and needing are closer to emotional states or conditions than they are to actions.
M-W notes, however, that while it considers these usages standard English, most of its evidence comes from speech rather than writing. And as we said earlier, many other commentators, including the editor of The New Fowler’s Modern English Usage, consider phrases like “want bad” and “need bad” to be informal rather than standard.
That’s why we advise you to pick your words according to context: conversation, casual writing, or formal written English. In any case, you can’t go wrong with “want badly.” Interestingly, at one time “want badly” was considered grammatically incorrect!
It was criticized by commentators in the early 1900s, apparently because they didn’t like the use of “badly” as an intensifier meaning “very much.” - This is no longer the case. Here’s what The American Heritage Dictionary of the English Language (4th ed.) has to say on the subject:
“The use of badly with want was once considered incorrect but is now entirely acceptable: We wanted badly to go to the beach.”
There are two lessons here. One is that nobody will criticize you for saying “want badly.” The other is that English is a changing language. Stay tuned.
