1. "Principal Phrase": This term doesn't exist in standard grammar. It's possible you heard it in a specific context, like a particular teaching style or a specific linguistic theory. If you provide more context, I can help figure out what it might mean.
2. "Prepositional Phrase": This is a very common grammatical structure. A prepositional phrase consists of a preposition (like "on", "in", "at", "to", "from", "with", "by") followed by its object, which is usually a noun or pronoun.
* Example: The cat sat on the mat. ("on the mat" is the prepositional phrase)
3. "Principle Clause": This is an informal term used to refer to the main clause in a sentence. It's the part of the sentence that contains the subject and the verb and expresses the main idea.
* Example: "The cat sat on the mat because it was tired." ("because it was tired" is the principle clause - it's the most important part of the sentence)
4. "Phrase with a Principle Word": This is a more general term that could describe any phrase that contains a key word or concept that is important to understanding the phrase's meaning.
* Example: "The principle of justice is essential for a fair society." ("principle of justice" is the phrase, and "principle" is the key word)
5. "Principle as a Modifier": A principle can sometimes act as an adjective modifying a noun.
* Example: "They followed the principled path." ("principled" is a modifier describing the "path")
Please clarify your question by providing more context, and I can give you a more accurate answer.