The word Tajwīd comes from the Arabic root word ج وَّد (jawwada) which literally means, “To make better/correct”.
Tajwīd can thus be said to mean:
“To pronounce every letter correctly; pronouncing every letter from its correct articulation point (makhraj) and with its correct characteristics (ṣifāt).”
Reciting the Holy Qur’ān with Tajwīd is farḍ ‘ayn (individual obligation - farḍ on each and every person).
The Holy Qur’ān is not an ordinary book but the Words of Allāh. Therefore, one must pay complete attention to the way one recites the Holy Qur’ān.
The Arabic of the Qur’ān in particular (and Arabic in general) is both very sophisticated and sensitive; the slightest alteration in the pronunciation of a letter may change the meaning entirely; and sometimes these mispronunciations will give meanings that result in utterances of kufr (infidelity).