What part of speech is yelled and scream?

Both "yelled" and "scream" can be different parts of speech depending on how they are used in a sentence:

Yelled:

* Verb (past tense): This is the most common usage. Example: "She yelled at the dog."

* Adjective: This is less common but possible. Example: "His yelled words echoed through the hall."

Scream:

* Verb: This is the most common usage. Example: "The baby screamed when he dropped his toy."

* Noun: This refers to the act of screaming. Example: "The scream startled the neighbors."

In summary:

* Yelled is usually a verb (past tense), but can sometimes be an adjective.

* Scream is usually a verb, but can also be a noun.