Nominalizing verb with い-ending vs ーの


In my Japanese class today, we were supposed to say a sport we liked. I said:

> 泳ぎが好きです。

We haven't learned this way of nominalizing verbs or the names of many sports,
so my 先生 shook her head no and I said some other sport. I am aware that some
verbs are nominalized with this kind of ending (including 泳ぐ):

> 終わる → 終わり
>
> 話す → 話
>
> 始まる → 始まり
>
> 走る → 走り

So when is it appropriate to append の to nominalize a verb versus using the
い-ending as its nominalization?

* * *

Edit:

To be clear, I am asking what the difference in meaning is between the two
following statements:

> **泳ぎ** が好きです。
>
> **泳ぐの** が好きです。




To generically answer your question as described in your title, masu-stem (aka
連用形) can often "nominalize" a verb, but the resulting nouns can have
unpredictable meanings, and you have to learn them individually. Please see
[this answer](https://japanese.stackexchange.com/a/32311/5010). A good rule of
thumb is that you should avoid trying to nominalize a verb using 連用形 unless
you know what you are doing.

To specifically answer your question about the difference between 泳ぐの and 泳ぎ,
泳ぎ tends **not** to refer to the abstract concept of "swimming" as a kind of
sport or action. Instead, it usually refers to someone's concrete swimming
ability, style, form, episode, achievement, etc. 泳ぎが好きです simply sounds
unnatural to me. A normal way to say "I like swimming" is 水泳が好きです (sounds
relatively formal/serious) or 泳ぐのが好きです (sounds casual). 泳ぎ is also used as a
part of fixed compounds such as 平泳ぎ "breaststroke" and 背泳ぎ "backstroke".

You can use 泳ぎ like so:

  * 彼女の泳ぎはとても美しい。  
(彼女の水泳は美しい is very unnatural)

  * 彼の泳ぎは世界に感動を与えた。  
(彼の水泳は世界に感動を与えた is wrong)

  * 体操選手は脂肪が少ないため、泳ぎが苦手です。  
(this 泳ぎ is interchangeable with 泳ぐの or 水泳)

  * 今は平泳ぎを練習しています。  
(平泳ぎ is a fixed compound)

* * *

**EDIT:** How about other verbs? の is very consistent and straightforward:

  * ✅ 私は踊るのが好きです: I like dancing (either casually at a night club or seriously as a performance).
  * ✅ 私は歌うのが好きです: I like singing.
  * ✅ 私は走るのが好きです: I like running/jogging.
  * ✅ 私は絵を描くのが好きです: I like drawing pictures.

However masu-stems are inconsistent and tricky:

  * ✅ 私は踊りが好きです: I like (watching or doing) dance (performances).  
(踊り is basically a wago equivalent of ダンス.)

  * 私は歌いが好きです: wrong  
(although 歌い occasionally means 'singer' in compounds)

  * 私は走りが好きです: wrong  
(although 走り means 'running form/ability')

  * ❓ 私は絵描きが好きです: I like painters (people).




To generically answer your question as described in your title, masu-stem (aka
連用形) can often "nominalize" a verb, but the resulting nouns can have
unpredictable meanings, and you have to learn them individually. Please see
[this answer](https://japanese.stackexchange.com/a/32311/5010). A good rule of
thumb is that you should avoid trying to nominalize a verb using 連用形 unless
you know what you are doing.

To specifically answer your question about the difference between 泳ぐの and 泳ぎ,
泳ぎ tends **not** to refer to the abstract concept of "swimming" as a kind of
sport or action. Instead, it usually refers to someone's concrete swimming
ability, style, form, episode, achievement, etc. 泳ぎが好きです simply sounds
unnatural to me. A normal way to say "I like swimming" is 水泳が好きです (sounds
relatively formal/serious) or 泳ぐのが好きです (sounds casual). 泳ぎ is also used as a
part of fixed compounds such as 平泳ぎ "breaststroke" and 背泳ぎ "backstroke".

You can use 泳ぎ like so:

  * 彼女の泳ぎはとても美しい。  
(彼女の水泳は美しい is very unnatural)

  * 彼の泳ぎは世界に感動を与えた。  
(彼の水泳は世界に感動を与えた is wrong)

  * 体操選手は脂肪が少ないため、泳ぎが苦手です。  
(this 泳ぎ is interchangeable with 泳ぐの or 水泳)

  * 今は平泳ぎを練習しています。  
(平泳ぎ is a fixed compound)

* * *

**EDIT:** How about other verbs? の is very consistent and straightforward:

  * ✅ 私は踊るのが好きです: I like dancing (either casually at a night club or seriously as a performance).
  * ✅ 私は歌うのが好きです: I like singing.
  * ✅ 私は走るのが好きです: I like running/jogging.
  * ✅ 私は絵を描くのが好きです: I like drawing pictures.

However masu-stems are inconsistent and tricky:

  * ✅ 私は踊りが好きです: I like (watching or doing) dance (performances).  
(踊り is basically a wago equivalent of ダンス.)

  * 私は歌いが好きです: wrong  
(although 歌い occasionally means 'singer' in compounds)

  * 私は走りが好きです: wrong  
(although 走り means 'running form/ability')

  * ❓ 私は絵描きが好きです: I like painters (people).

