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?
Japanese Language Stack Exchange is a question and answer site for students, teachers, and linguists wanting to discuss the finer points of the Japanese language. It only takes a minute to sign up.Sign up to join this community
This is why "wa" is called a topic marker rather than a subject marker.
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.