What's the difference between 同然 and 同様?


As in the title, what is the difference between these two?

dictionary.goo.ne.jp says:

> [同然](http://dictionary.goo.ne.jp/leaf/jn2/156262/m0u/%E5%90%8C%E7%84%B6/):
> 同じであること。また、そのさま。同様。
>
> [同様](http://dictionary.goo.ne.jp/leaf/jn2/157033/m0u/%E5%90%8C%E6%A7%98/):
> 同じであること。ほとんど同じであること。また、そのさま。

and on the 類語 page these two are listed under [one
entry](http://dictionary.goo.ne.jp/leaf/thsrs/16964/m0u/%E5%90%8C%E7%84%B6/):

> 「同様」「同然」は、「同じ」「一緒」より、差異についての基準が緩い場合にほぼ似たような意味合いで用いられる。

yet, according to the table at the bottom there, [their usage seems to
differ](http://dictionary.goo.ne.jp/leaf/thsrs/16964/m0u/%E5%90%8C%E7%84%B6/)




I'd translate 同然 as "so similar that it can now be considered X" or "as if it
is X". It states there is effectively no difference between the two. E.g.
夫婦も同然の二人、もはや勝ったも同然だ.

同様 would be more generally, "in the same manner to X", e.g.
炭酸と同様の作用を有する、操作は先ほどと同様です

> 同性婚は認められていないものの、夫婦と同様の税制が適用される  
>  ... same tax rules are applied

.

> 同性婚は認められていないものの、夫婦同然の税制が適用される  
>  ... same tax rules are applied, such that there is essentially no
> difference between same-sex vs hetero-sex marriage.

`彼のと同然の靴` would be weird as you would be stating "the shoe can be considered
to be essentially his". When expressed more naturally, this will be
`彼の物であるも同然の靴`.




I'd translate 同然 as "so similar that it can now be considered X" or "as if it
is X". It states there is effectively no difference between the two. E.g.
夫婦も同然の二人、もはや勝ったも同然だ.

同様 would be more generally, "in the same manner to X", e.g.
炭酸と同様の作用を有する、操作は先ほどと同様です

> 同性婚は認められていないものの、夫婦と同様の税制が適用される  
>  ... same tax rules are applied

.

> 同性婚は認められていないものの、夫婦同然の税制が適用される  
>  ... same tax rules are applied, such that there is essentially no
> difference between same-sex vs hetero-sex marriage.

`彼のと同然の靴` would be weird as you would be stating "the shoe can be considered
to be essentially his". When expressed more naturally, this will be
`彼の物であるも同然の靴`.

