Why you cannnot use yes in affermative sentences but can not negative sentence?

You're close! The situation is a little more nuanced than that. It's not that you *can't* use "yes" in affirmative sentences, it's just that it's not the typical way to form an affirmative sentence.

Here's a breakdown:

"Yes" as an Affirmation:

* In direct answers: You use "yes" to affirmatively answer a question, often as a simple reply:

* "Are you coming to the party?" "Yes."

* "Do you like pizza?" "Yes."

* In emphasis: "Yes" can be used for emphasis in an affirmative sentence:

* "I do like pizza. Yes, I love it!"

* "You are coming, yes?"

Why "Yes" isn't Usually in Affirmative Sentences:

* Redundancy: "Yes" is already implied by the affirmative construction of the sentence. It's like saying "I am going to the party, yes" - the "yes" is unnecessary.

* Grammar: In standard English, we typically use the subject-verb structure to convey affirmation, rather than starting with "yes."

Examples:

* Affirmative: "I am going to the party."

* Negative: "I am not going to the party."

* Question: "Are you going to the party?"

* Answer using "yes": "Yes."

Important Note: While it's not the usual structure, you *can* use "yes" in an affirmative sentence for stylistic effect, to add emphasis, or for a particular tone. However, it's not generally considered grammatically correct in standard English for forming an affirmative sentence.