tamago o yoku tabemasu


> tamago o yoku tabemasu.
>
> kudamono wa amari tabemasen.

Why for the first sentence with tamago, the particle "o" is used where as for
the second sentence with kudamono, particle "wa" is used?




This is why "wa" is called a _topic_ marker rather than a _subject_ marker.

> ### [Topic
> Marker](https://en.wikipedia.org/wiki/Topic_marker#Japanese:_%E3%81%AF)
>
> The topic marker is one of many Japanese particles. It is written with the
> hiragana は, which is normally pronounced _ha_ , but when used as a particle
> is pronounced _wa_. **It is placed after whatever is to be marked as the
> topic.** If what is to be the topic would have had が (ga), the subject
> marker, or を ((w)o), the direct object marker, as its particle, those are
> replaced by は. Other particles (for example: に, と, or で) are not replaced,
> and は is placed after them. (emphasis mine)

は marks the subject of a sentence only in, say, 80% of the cases. In your
case, を was replaced by は because fruit is the (contrasted) topic of the
second sentence. Note that this は is also working as a contrast marker. Also
note that は is much preferred in negative sentences.

See:

  * [What's the difference between wa (は) and ga (が)?](https://japanese.stackexchange.com/q/22/5010)
  * [Why is the topic marker often used in negative statements (ではない, ～とは思わない)?](https://japanese.stackexchange.com/q/1077/5010)




This is why "wa" is called a _topic_ marker rather than a _subject_ marker.

> ### [Topic
> Marker](https://en.wikipedia.org/wiki/Topic_marker#Japanese:_%E3%81%AF)
>
> The topic marker is one of many Japanese particles. It is written with the
> hiragana は, which is normally pronounced _ha_ , but when used as a particle
> is pronounced _wa_. **It is placed after whatever is to be marked as the
> topic.** If what is to be the topic would have had が (ga), the subject
> marker, or を ((w)o), the direct object marker, as its particle, those are
> replaced by は. Other particles (for example: に, と, or で) are not replaced,
> and は is placed after them. (emphasis mine)

は marks the subject of a sentence only in, say, 80% of the cases. In your
case, を was replaced by は because fruit is the (contrasted) topic of the
second sentence. Note that this は is also working as a contrast marker. Also
note that は is much preferred in negative sentences.

See:

  * [What's the difference between wa (は) and ga (が)?](https://japanese.stackexchange.com/q/22/5010)
  * [Why is the topic marker often used in negative statements (ではない, ～とは思わない)?](https://japanese.stackexchange.com/q/1077/5010)

