Assalaam alaikum wa rahmatullah
Which is the correct terminolgy Iste'la (musta'lia) or Mufakkham?
is a characteristic and it is a right of the letter that is present in the letters that form the phrase in all states, regardless of which vowel the letter has. Tafkheem is a due of the letter and the tafkheem level varies according to the vowel of the letter. Both terminologies are correct to use but it depends on the grammatical place of the word in the sentence. The characteristics itself is , the letter that has this characteristic is called . Similarly, if we describe by its level of tafkheem then we say the letter is mufakkham. All letters of have tafkheem or are , but there are other letters that do not have the characteristic of , but have tafkheem under certain circumstances. When any letter has tafkheem, we can say the letter is . All letters of isti’laa have tafkheem but not all letters that have tafkheem are . Please see: http://www.abouttajweed.com/tafkheem-and-tarqeeq/index.php .