This sentence includes an interrupting phrase (a phrase that is not grammatically relevant to the clause in which it appears) that adds information to the sentence. This phrase needs to be included within commas, as such the best way to correct the underlined portion above is, "The great general, once feared by all of his enemies, had become weak in his old age."

Introductory phrases precede and are subordinate to a sentence's main clause. Introductory phrases add information to a sentence, but are not necessary to the sentence being grammatically complete, and such clauses must be separated from the rest of the sentence with a comma. In the example sentence, "still my favorite student" is an introductory phrase. The best way to correct the underlined portion above is, "Still my favorite student, Paul never fails to impress with his magnificent essay writing."

Introductory phrases precede and are subordinate to a sentence's main clause. Introductory phrases add information to a sentence, but are not necessary to the sentence being grammatically complete, and such clauses must be separated from the rest of the sentence with a single comma. In the sentence above, "While I find it difficult to concentrate when Sheila sings" is acting as such an introductory phrase, so a comma needs to be added after "sings" in order for the sentence to be grammatically correct. Note that a semicolon must follow and precede an independent clause, and can never be used to punctuate a dependent clause.

Interrupting phrases are subordinate and add information to a sentence, but are not necessary to the sentence being complete. Such phrases must be separated from the rest of the sentence by commas. The example sentence is missing both of these necessary commas. The best way to correct the underlined portion above is, "Jesus Christ, one of the most influential figures of the last millennium, is a central figure in Christianity."

Interrupting phrases are subordinate and add information to a sentence, but are not necessary to the sentence being complete. Such phrases must be separated from the rest of the sentence by commas. In the example sentence a comma correctly precedes the interrupting phrase, but does a second comma does not correctly close it off. The corrected version reads, "Jerry, one of the richest comedians in the world, is really not very funny at all."

Interrupting phrases provide information or context about an element of a sentence, but are not necessary to the sentence being complete. Because they come in the middle of a clause such phrases must be separated from the rest of the sentence by commas. The example sentence places the first comma at the beginning of this interrupting phrase, but fails to place the necessary comma the end. The best way to correct the underlined portion above is, "Larry, one of my all time favorite comedians, has an incredibly funny show in development."

Introductory phrases precede and are subordinate to a sentence's main clause. Introductory phrases add information to a sentence, but are not necessary to the sentence being grammatically complete, and such clauses must be separated from the rest of the sentence with a comma. In this case "If you don't stop interrupting my class," is a dependent, introductory clause, and as such should not be punctuated with a semicolon.

Interrupting phrases add information to a sentence but are not necessary to the sentence being complete, must be separated from the rest of the sentence by commas. The example sentence is missing two commas. The best way to correct the underlined portion above is, "Paul, my old yellow lab, is in good health in spite of his advanced years."

Sometimes important context or information pertaining needs to be added to the sentence, but the author may not wish to integrate this information into the fundamental grammatical structure of the sentence. In these instance, such information can be contained in what are called interrupting phrases, these are words or sets of words that interrupt a clause, but exist outside of the fundamental structure of that clause. Interrupting phrases must be enclosed with commas. The best version of the example sentence reads, Paulus Atredies, one of the greatest men who ever lived, died fighting a bull in a dirty pit.

Introductory phrases precede and are subordinate to a sentence's main clause. Introductory phrases add information to a sentence, but are not necessary to the sentence being grammatically complete, and such clauses must be separated from the rest of the sentence with a comma. In the example sentence, "When Franklin treats his mother that way," acts as such an introductory phrase.