Question

Some of the letters are pronounced from the same articulation point but yet sound different. Why?

Answer

The characteristics of letters are what differentiate one letter from another when the two share the same articulation point.  If two letters shared the same articulation point and sounded the same, they would not be two different letters, but would be one and the same.  The characteristics of the letters will, insha’ Allah, be discussed in future tidbit lessons on this site.  They are a very important part of tajweed.