What part of speech is not appropriate in formal writing but often used daily conversation?

The part of speech that's often used in daily conversation but is generally considered inappropriate in formal writing is contractions.

Here's why:

* Formal writing aims for a more elevated and polished tone. Contractions, by nature, shorten words and can sometimes sound casual or even sloppy.

* Formal writing emphasizes clarity and precision. Contractions can sometimes lead to ambiguity, especially when dealing with complex ideas or legal documents.

Examples:

* Informal: "I'm going to the store."

* Formal: "I am going to the store."

* Informal: "It's a beautiful day."

* Formal: "It is a beautiful day."

However, it's important to note that there are some exceptions:

* Contractions can be used in formal writing when they appear in quotes. For example, if you are quoting someone who uses contractions.

* Certain contractions, like "don't" and "can't," are considered acceptable in formal writing, particularly when used in specific contexts.

Overall, it's best to err on the side of caution and avoid contractions in formal writing unless you are absolutely certain it is appropriate.