One who wishes to learn a science needs to know its principles so that he will gain insight into the sought science.  There are several principles in the science of tajweed that should be understood:

1.  Its definition

By linguistic definition: Betterment
Applied definition: Articulating every letter from its articulation point and giving the letter its rights and dues of characteristics.

Rights of the letters are its required characteristics that never leave it.  The dues of the letters are its presented characteristics that are present in it some of the time, and not present at other times.  i.e. the medd, idgham

2.  Its formation

The words of the Glorious Qur'an and some said Honorable Hadiths also.

3. Its fruits

It is preserving the tongue from mistakes in pronunciation of the Glorious Qur'an during reading.

4.  Its precedence

It is one of the most honored of sciences and one of the best of them due to its relation to Allah’s words.

5.  Its place within the sciences

It is one of the Islamic Law sciences that are related to the Glorious Qur'an.

6.  Its founder

The rule setter from the practical point of view is the Messenger of Allah because the Qur'an was revealed to him from Allah, the most High, with tajweed, and he, was instructed on it from the Trustworthy, Jibreel, peace be upon him, and taught it to his companions, who then taught it to their followers and so on until it came to us by these chains.  The rule setters from the scientific point of view are the scholars of Qur'anic sciences, such as Abu 'Ubaid Al-Qasim bin Sallaam.

7.  Its precept

Knowledge of tajweed is fardh kifayaah, meaning some of the Muslim community must know it, and its application is fardh ‘ain, required by all Muslims (men and women) who have the complete Qur'an or part of it memorized, even if only one surah.

8.  Reasons for its rules

Guarding the Glorious Qur'an and preserving it from distortion.  The Arabs mixed with non-Arabs after the spread of Islam, and the Muslims feared that the Arab tongue would become corrupted with this intermixing.  It then became mandatory for rules to be put down that would preserve the recitation of the Qur'an from mistakes, and guarantee the reader of the Qur'an integrity of pronunciation.

9.  Its principles

The knowledge of tajweed is contingent on four matters:

1. Knowledge of the articulation points of the letters
2. Knowledge of the characteristics of the letters
3. Knowledge of what rules change in the letters due to the order of letters
4. Exercising the tongue and a lot of repetition.