[Grammar] what does "deadly" means in both sentences?

[Halum gh]

I have been trying the quizzes contained in Using English lately, when i was passing the Adverb with 2 Forms passage, i got problem to understand 2 question. the first one is the sentence "It's deadly serious." Why is it true in grammatical and what does deadly mean here?, and the second one is the sentence "I am deadly sure." why is it false in grammatical and what does deadly mean here?
Both sentences are look seems to me, but why the first is true and another one is false?
thank you

 

[teechar]

Hello Halum, and welcome to the forum.

I have been trying the quizzes [STRIKE]contained in[/STRIKE] on UsingEnglish lately, but when I was [STRIKE]passing[/STRIKE] doing the Adverb with 2 Forms passage, I got a problem [STRIKE]to[/STRIKE] and couldn't understand two questions. The first one is the sentence "It's deadly serious." Why is it [STRIKE]true in[/STRIKE] grammatical, and what does "deadly" mean here?

It's grammatical; "deadly" is an adverb meaning extremely.

And the second one is the sentence "I am deadly sure." Why is it [STRIKE]false in grammatical[/STRIKE] incorrect, and what does "deadly" mean here?

Both sentences are look the same [STRIKE]seems[/STRIKE] to me, but why is the first correct but not the second?[STRIKE]is true and another one is false?[/STRIKE]
Thank you.

That's a good question. The second sentence is incorrect because "deadly" does not collocate naturally with "sure." Instead, you can say "I'm dead sure." In that case, "dead" is an adverb meaning "very." Natural collocation is not an easy thing for new language learners, and many find it daunting. However, you'll find that you'll get better and better at it with more practice.

Here are some useful websites that can help a bit with that.

www.fraze.it
You can enter what you want to check on in the search box, for example, "deadly sure" (with the quotation marks), and see the results you get.

http://miscollocation-richtrf.rhcloud.com/
This one checks verb-noun collocations.