Question: *Life* is singular but the noun *adventures* is plural, so which sentence is correct? 

> 
> * *Life full of adventures are waiting for us.*
> * *Life full of adventures is waiting for us.*
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Answer: 
We are talking about ***life*** which is singular and using verb ***is*** for some.

Hence it should be: **Life full of adventures is waiting for us.**

If we were using verb for plural form of a noun then it will be ***are***.
Try some basic variations to get the answer. 

> 
> "A great life is waiting for **me**"  
> 
>  "A life which is great is waiting for me"  
> 
>  "An adventurous life is waiting for me"  
> 
>  "A life, which is full of adventures, is waiting for me"  
> 
> **"A life, full of adventures, is waiting for me"**  
> 
>  Singular "life" (with Singular "me") : use Singular "is".
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Now, this Question mentions "waiting for **us**", which slightly complicates the Issue. Is it still referring to one life or many lives ? If it had been "a house" , then many persons can still occupy it, but each person requires his own life.

> 
> **"A house, full of toys, is waiting for us"**  
> 
>  Singular "house" (with Plural "us") : use Singular "is".
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In case of "life", each person requires his own life, but there may be some cases (eg husband & wife or parents & children) where the "life" is joined and shared.

> 
> (A) **"A life, full of adventures, is waiting for us"**  
> 
>  Singular "life" (with Plural "us") : use Singular "is".
> 
> 
> (B) **"Lives full of adventures are waiting for us"**  
> 
>  Plural "lives" (with Plural "us") : use Plural "are".
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**Conclusion** : Depending on **context**, (A) or (B) can be taken as valid answers or alternatives to this Question.