salam, please can you explain what Al-lahm is and give some examples. jzk
Answer
Wa alaikum assalaam wa rahmatullahi wa barakatuh,
Most likely you mean
, with a 
as the last letter. The word linguistically means a mistake. In applied tajweed, it means a mistake and deviation from correctness when reading. is divided into two categories in tajweed:1.
is an obvious and clear mistake. It is a mistake that occurs in the pronunciation of the that affects the accuracy of the reading. An example of this would be reading the letter 
as a 
.2.
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. An example of this would be to not hide a
saakinah when followed by one of the letters of ikhfa', or not lengthen the 
four vowel counts.