Is by himself a prepositional phase?

No, "by himself" is not a prepositional phrase. It is an adverbial phrase.

Here's why:

* Prepositional phrases start with a preposition and end with a noun or pronoun called the object of the preposition. For example, "in the box," "on the table," "with a smile."

* Adverbial phrases modify verbs, adjectives, or other adverbs, providing information about how, when, where, or to what extent something happens. "By himself" tells us how the action is being performed.

Example:

* "He walked by himself." Here, "by himself" modifies the verb "walked" and tells us how he walked.

Let me know if you have more questions!