Question

Salaam:
I was browsing through a tajweed book and notice that the LAM NOON and RA are in the same place of origin group called AL-HURUF AL-DHAULAQIYYAH.  I notice you don't have the LAM in the group as the RA and NOON . Why is that?
Thank for your time

Answer

Wa alaikum assalaam wa rahmatu Allahi wa barakatuh. 

There is no particular reason that we did not group all the letters into their specific groups in the articulation point lessons outside of that we like to make each lesson short to medium in length.  We also did not wish to get too much terminology involved, since the terms are meaningful to those who know Arabic, but not necessarily so to those who do not.

We put the articulation point of the letter  and  in the same lesson to emphasize that they both use the sides of the tongue.  Nonetheless, the are named thus because all three letters the ,  and use the  or tip of the tongue.  This does not mean that they have the same exact articulation point (according to the majority of the scholars) but are very close to each other. 

You are most welcome.