Why 余計 here is not proper: 余計があったら、ひとつ貸してもらえませんか。

[Pinutile]

余計があったら、ひとつ貸してもらえませんか。 ( false ) (N2 問題例)

Why is this sentence an improper use of 余計 ? Isn't it can be used to express "more than necessary"(so you can lend me some)? Can yokei be used as a noun? Maybr that explains but 大辞林 labelled it as 名 ・形動? 

I'm a beginner of Japanese and have difficulties in reading monolingual Japanese dictionary. Please help me, many thanks!!

[宇崎ちゃん]

It's actually impressive that you're a beginner and now already learn N2 level Japanese.
N2 is a level I didn't reach yet, so I help you with this one.
Here's a useful link for you (it's an online Japanese dictionary, explaining everything in English): http://jisho.org/word/%E4%BD%99%E8%A8%88

[Pinutile]

  On 12/3/2015 at 6:43 PM, Blaveloper said:

It's actually impressive that you're a beginner and now already learn N2 level Japanese.
N2 is a level I didn't reach yet, so I help you with this one.
Here's a useful link for you (it's an online Japanese dictionary, explaining everything in English): http://jisho.org/word/%E4%BD%99%E8%A8%88

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Sorry! I didn't notice this reply until now.

In some way I'm not an absolute beginner, since I began taking a Japanese course two years ago and achieved at least N3 level. But compared to a fluent mastery, I thought "beginner" is a suitable label for me. (And due to limited time for oral drils, I always do much worse in speaking and writing than in reading.)

As for dictionaries, recently I gradually became capable of using monolingual Japanese dictionary such as the prestigious 大辞林. (an online version: https://kotobank.jp/) And thank you for your recommendation!

[DidiMihova]

  On 12/3/2015 at 5:17 PM, Pinutile said:

余計があったら、ひとつ貸してもらえませんか。 ( false ) (N2 問題例)

Why is this sentence an improper use of 余計 ? Isn't it can be used to express "more than necessary"(so you can lend me some)? Can yokei be used as a noun? Maybr that explains but 大辞林 labelled it as 名 ・形動? 

I'm a beginner of Japanese and have difficulties in reading monolingual Japanese dictionary. Please help me, many thanks!!

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I know that many years past since this was posted, but in case there is someone wondering the mistake is that 余計 is a な形容詞 na-adjective and you need a noun to connect it with 
余計なこと言わないで。

In 余計があったら、ひとつ貸してもらえませんか。余計 has been used as noun which it is not. But I also don't think 余計 is a good choice at all. 

Maybe the sentence would be better as 使わないなら、ひとつ貸してもらえませんか。