I was writing a composition in Japanese, and since I wanted to give reasons I
wrote the following:

僕は日本語の会話がまだできないし、友達は英語が上手 **し** 、日本語を少ししか練習しませんでした。

However, I got corrected like this:

僕は日本語の会話がまだできないし、友達は英語が上手 **なので** 、日本語を少ししか練習しませんでした。

I don't understand why I can't use し or why it's better ので in this context.
Can anyone explain me the reason?
CC BY-SA 3.0
2016-11-18T07:58:21.783
40981
2016-12-10T12:50:14.050
2016-12-10T12:50:14.050
10859
14270
question
grammar particles
I got corrected 上手し for 上手なので, but why?
> 友達は英語が上手 **し** 、

I'm afraid 「[上手]{じょうず}し」/「[上手]{うま}し」 is incorrect.

I think you could use ～し, ～ので, or ～から here. You could say like this, using the
na-adjective [上手]{じょうず}な:

> [上手]{じょうず} **だ** し、  
>  上手なので、  
>  上手だから、

or, using the i-adjective [上手]{うま}い:

> [上手]{うま} **い** し、  
>  上手いので、  
>  上手いから、

「～し」 and 「～から」 would sound more casual than 「～ので」.
CC BY-SA 3.0
2016-11-18T08:43:46.013
40983
2016-11-18T08:51:48.993
2016-11-18T08:51:48.993
9831
9831
40981
answer
上手し is wrong. It must be 上手だし.

According to "A Dictionary of Basic Japanese Grammar", page 396, na-adjectives
and nouns must be followed by だし (or だったし if it is the past tense).  

Examples:  
先生だし (noun + だし)  
綺麗だし (na-adjective + だし)

Grammatically that is the only mistake.

You teacher used ので probably just to make it clear that it implies a reason or
cause.  
し, on the other hand, does not imply reason or cause, it is just an emphatic
"and".
CC BY-SA 3.0
2016-11-18T15:42:16.457
40989
2016-11-22T05:59:18.087
2016-11-22T05:59:18.087
9831
18157
40981
answer