Question

What is the linguistic meaning of tajweed?

What is lahan jalee and lahan khafee?

Answer

Assalaam alaikum. 

The linguistic meaning of tajweed is: Betterment. 
The applied definition of tajweed is:  Articulating every letter from its articulation point and giving the letter its rights and dues of characteristics. 

 is an obvious and clear mistake. It is a mistake that occurs in the pronunciation of the that affect the accuracy of the reading.

 is an obscured and hidden mistake.  It is a mistake that enters the reading but is only heard and known by an accomplished reader.  It is not a mistake that leads to a change in the meaning, or language, or grammar. 

Wa assalaam