Sentences with set-off parts; intonation and punctuation

Sometimes the speaker feels a part of the sentence is not clear enough and adds next to it another part with the same function to explain it. Such a part, which explains and specifies the preceding part, is called a set-off explanatory part. For example, in “Biz safarni o‘sha yerdan boshladik” the words “o‘sha yerdan” are vague; if we say “Biz safarni o‘sha yerdan, ya’ni Xivadan, boshladik”, the meaning becomes clear. There are four kinds of set-off parts: set-off object, attribute, hol and appositive. A set-off appositive comes after the word it explains, often refers to the subject and is said with special intonation: “Nodira opa, kimyo o‘qituvchimiz, sinfga kirdi”.