The difference between は and を?


Hello everyone as the title states I am having difficulty understanding when
to use the correct particle.

As an example

> 肉は食べません (I do not eat meat)

and

> やさいを食べます (I eat vegetables)

Is it acceptable to use both wa or o in both these sentences? Wouldn't the
first sentence be more correct if I were to say 私は肉を食べません. The reason I chose
these two specific sentences is because I saw them in a book. I can not
understand why in one sentence they used は while in the other they used を even
though they have the same basic structure.

Thank you for any help you may provide!




> [野菜]{やさい} **を** 食べます。 vs 野菜 **は** 食べます。

_Grammatically speaking_ , both are correct. They're different in meaning and
usage.

を is the object marker. 野菜を食べます is usually an unmarked statement to say "I
eat/someone eats vegetables". The は can be, roughly speaking, the topic
particle (主題の「は」) or the contrastive particle (対比の「は」). For example, you can
use them this way:

> 「普段、朝食に何を食べますか？」--「野菜 **を** 食べます。」(not は)  
>  "What do you usually have for breakfast?" -- "I have vegetables."  
>  「鈴虫は何を食べますか？」--「ナスやキュウリなどの野菜 **を** 食べます。」(not は)  
>  "What do bell crickets eat?" -- "They eat vegetables such as aubergine and
> cucumber."

Here, the を marks new information (新情報).

> 「普段、野菜は食べますか？」--「はい、野菜 **は** たくさん食べます。」(not を)  
>  "Do you eat vegetables regularly?" -- "Yes, ( _lit._ As for vegetables, I
> eat a lot. →) I eat a lot of vegetables."

The は is the so-called "topical/thematic は". Here, it marks old/known
information (旧情報/既知情報).

は can also be used this way:

> 「野菜 **は** 食べます。でも肉 **は** 食べません。」  
>  "I eat vegetables. But I don't eat meat."  
>  「鈴虫は*、肉 **は** 食べませんが、野菜 **は** 食べます。」  
>  "Bell crickets don't eat meat, but they eat vegetables."  
>  *The は in 鈴虫は is a topic marker; there can be only one topical は in a
> clause. If you see two は's in one clause, at least one of them should be
> contrastive.

The は here is the so-called "contrastive は". (You could refer to this thread
for more about the contrastive は: [What's the difference between wa (は) and ga
(が)?](https://japanese.stackexchange.com/q/22/9831))

* * *

> 肉 **は** 食べません。 vs 肉 **を** 食べません。

Again, they're both _grammatically_ correct, and different in meaning and
usage.

The は can be topical/thematic:

> 「お肉はよく召し上がりますか？」--「いいえ、肉 **は** まったく食べません。」(not を)  
>  "Do you eat meat often?" -- "No, I don't eat meat at all."

The contrastive は is also used to mark or highlight the negated element in a
sentence:

> 普段、朝食に肉 **は** 食べません。  
>  I usually don't have meat for breakfast (can imply: but I have something
> else).  
>  普段、朝食に **は** 肉を食べません。  
>  I usually don't have meat for breakfast (can imply: but I do for dinner).  
>  普段 **は** 、朝食に肉を食べません。  
>  I usually don't have meat for breakfast (can imply: but I do today).

Here, the は shows the scope of negation: 肉を* is negated in the first sentence,
and 朝食に is negated in the second, and so on.  
* When 「XXを」 or 「XXが」 is marked with a は, the は replaces the が or を, as in 「XXは」 rather than 「XXをは」「XXがは」.  
There usually is some negated element in a negative sentence, and therefore
you'll more frequently see a は in a negative sentence.

As for the example using an を, you'd use it in a context like this:

> 「子どもの好き嫌いが激しくて…。」--「何を食べてくれないんですか？」--「野菜 **を** ぜんぜん食べないんです。」(not は)  
>  "My child is so picky about food..." -- "What does s/he not eat?" -- "S/he
> doesn't eat vegetables at all."  
>  You'd reply with 「～を」「～が」「～に」「～と」「～から」 etc., not 「～は」「～には」「～とは」「～からは」 etc.
> to questions 「何を」「何が」「どこに」「誰と」 etc., as in: 「何がないんですか？」「消しゴム **が**
> ないんです。」(not は) / 「誰と連絡がつかないんですか？」「山田さん **と** 連絡がつかないんです。」(not とは）




> [野菜]{やさい} **を** 食べます。 vs 野菜 **は** 食べます。

_Grammatically speaking_ , both are correct. They're different in meaning and
usage.

を is the object marker. 野菜を食べます is usually an unmarked statement to say "I
eat/someone eats vegetables". The は can be, roughly speaking, the topic
particle (主題の「は」) or the contrastive particle (対比の「は」). For example, you can
use them this way:

> 「普段、朝食に何を食べますか？」--「野菜 **を** 食べます。」(not は)  
>  "What do you usually have for breakfast?" -- "I have vegetables."  
>  「鈴虫は何を食べますか？」--「ナスやキュウリなどの野菜 **を** 食べます。」(not は)  
>  "What do bell crickets eat?" -- "They eat vegetables such as aubergine and
> cucumber."

Here, the を marks new information (新情報).

> 「普段、野菜は食べますか？」--「はい、野菜 **は** たくさん食べます。」(not を)  
>  "Do you eat vegetables regularly?" -- "Yes, ( _lit._ As for vegetables, I
> eat a lot. →) I eat a lot of vegetables."

The は is the so-called "topical/thematic は". Here, it marks old/known
information (旧情報/既知情報).

は can also be used this way:

> 「野菜 **は** 食べます。でも肉 **は** 食べません。」  
>  "I eat vegetables. But I don't eat meat."  
>  「鈴虫は*、肉 **は** 食べませんが、野菜 **は** 食べます。」  
>  "Bell crickets don't eat meat, but they eat vegetables."  
>  *The は in 鈴虫は is a topic marker; there can be only one topical は in a
> clause. If you see two は's in one clause, at least one of them should be
> contrastive.

The は here is the so-called "contrastive は". (You could refer to this thread
for more about the contrastive は: [What's the difference between wa (は) and ga
(が)?](https://japanese.stackexchange.com/q/22/9831))

* * *

> 肉 **は** 食べません。 vs 肉 **を** 食べません。

Again, they're both _grammatically_ correct, and different in meaning and
usage.

The は can be topical/thematic:

> 「お肉はよく召し上がりますか？」--「いいえ、肉 **は** まったく食べません。」(not を)  
>  "Do you eat meat often?" -- "No, I don't eat meat at all."

The contrastive は is also used to mark or highlight the negated element in a
sentence:

> 普段、朝食に肉 **は** 食べません。  
>  I usually don't have meat for breakfast (can imply: but I have something
> else).  
>  普段、朝食に **は** 肉を食べません。  
>  I usually don't have meat for breakfast (can imply: but I do for dinner).  
>  普段 **は** 、朝食に肉を食べません。  
>  I usually don't have meat for breakfast (can imply: but I do today).

Here, the は shows the scope of negation: 肉を* is negated in the first sentence,
and 朝食に is negated in the second, and so on.  
* When 「XXを」 or 「XXが」 is marked with a は, the は replaces the が or を, as in 「XXは」 rather than 「XXをは」「XXがは」.  
There usually is some negated element in a negative sentence, and therefore
you'll more frequently see a は in a negative sentence.

As for the example using an を, you'd use it in a context like this:

> 「子どもの好き嫌いが激しくて…。」--「何を食べてくれないんですか？」--「野菜 **を** ぜんぜん食べないんです。」(not は)  
>  "My child is so picky about food..." -- "What does s/he not eat?" -- "S/he
> doesn't eat vegetables at all."  
>  You'd reply with 「～を」「～が」「～に」「～と」「～から」 etc., not 「～は」「～には」「～とは」「～からは」 etc.
> to questions 「何を」「何が」「どこに」「誰と」 etc., as in: 「何がないんですか？」「消しゴム **が**
> ないんです。」(not は) / 「誰と連絡がつかないんですか？」「山田さん **と** 連絡がつかないんです。」(not とは）

