dear i've found a cambridge book of speaking
i want to know if this book are good
thank you
5jj is not kidding you. It might be common to call each other "dear" in Algeria while practicing English with your friends (and posts here suggest that it is), but calling an English native "dear" could be taken as an insult, bad manners, or at least a strange lack of knowledge of the culture of which you are learning the language. In certain situations, it could also be construed as a homosexual overture. Please take note.
Writing "Dear Mr Smith" at the start of a letter is an
entirely different thing, and is normal. But when you meet Mr Smith, you do
not call him "dear", as in "Let's get some coffee, dear."
In America (mostly), it is possible to begin a speech with "Dear Friends". This is mostly done by people who want something from you, usually your money or your votes.
If you don't understand this, there are many of us who would be prepared to elaborate further. But the rule is quite simple. Don't do it.
PS: "Dear Teachers" is also acceptable to some of us, as being in the class of "Dear Mr Smith", but "Dears", or "dear" are not. This might seem to be too subtle a difference to have practical significance, but I'd like to join 5jj in assuring you that it is not.