replacing もの (noun) with もん (noun)


There are many usages of もん, but the one I am interested in is using もん to
replace もの (tangible noun). For example:  

`安いもん` (lit translation: cheap stuff) can be used to replace `安いもの`

The question is, can it be used to modify a sentence into a noun in a complex
sentence? For example:

`このナイフは安いもんが結構鋭いわよ` (Notice that the もん modifies the sentence into a noun in a
complex sentence)

If I recall correctly, this is grammatically wrong because もん can only replace
もの if and only if it is at the end of the sentence. For example, the sentence
`このナイフは安いもん` is grammatically correct, but not `このナイフは安いもんが結構鋭いわよ`.

I realize that one will still definitely understand the meaning of the
sentence perfectly well, but is this structure actually ever used?




You're right that もの(物) "thing" "stuff" can be contracted to もん, eg 安い[物]{もの},
[良]{い}い[物]{もの}, 欲しい[物]{もの} → 安いもん, いいもん, 欲しいもん etc. in colloquial speech,
especially in Kansai.

> このナイフは安いもん

It makes sense, but grammatically speaking it's not a _full_ sentence; to say
"This knife is cheap stuff", you need a copula だ/です at the end.

> このナイフは安い物です。  
>  このナイフは安いもんだ。

... but [安物]{やすもの} would be more common/natural in this case:

> このナイフは安物です。  
>  このナイフは安もんだ。

* * *

> "This knife is cheap stuff, **but** it is pretty sharp"  
>  このナイフは安いもん **が** 結構鋭いわよ。

The conjunctive particle が ("but") should be attached to the terminal form
(終止形) of a verb, adjective, etc., like this:

> このナイフは安物 **です** が、結構鋭いですよ。  
>  このナイフは安物/安もん **だ** が、結構鋭い。

Or more colloquially:

> このナイフ、安もんだけど、結構鋭いわよ。




You're right that もの(物) "thing" "stuff" can be contracted to もん, eg 安い[物]{もの},
[良]{い}い[物]{もの}, 欲しい[物]{もの} → 安いもん, いいもん, 欲しいもん etc. in colloquial speech,
especially in Kansai.

> このナイフは安いもん

It makes sense, but grammatically speaking it's not a _full_ sentence; to say
"This knife is cheap stuff", you need a copula だ/です at the end.

> このナイフは安い物です。  
>  このナイフは安いもんだ。

... but [安物]{やすもの} would be more common/natural in this case:

> このナイフは安物です。  
>  このナイフは安もんだ。

* * *

> "This knife is cheap stuff, **but** it is pretty sharp"  
>  このナイフは安いもん **が** 結構鋭いわよ。

The conjunctive particle が ("but") should be attached to the terminal form
(終止形) of a verb, adjective, etc., like this:

> このナイフは安物 **です** が、結構鋭いですよ。  
>  このナイフは安物/安もん **だ** が、結構鋭い。

Or more colloquially:

> このナイフ、安もんだけど、結構鋭いわよ。

