Are the designations "observant Muslim" and "non-observant Muslim" legitimate and correct, and what is the definition of a Muslim?

A Muslim is one who believes in the six pillars of faith and pronounces the two testimonies of faith. Such a person has the rights of Muslims and bears their responsibilities, unless they invalidate their Islam with a nullifier. People vary in their degrees of faith and righteous deeds; among them are those who wrong themselves, those who are moderate, and those who are foremost in good deeds.

There is no harm in using terms like "committed" (multazim) and "uncommitted" (ghair multazim), provided that the concept of commitment is not reduced solely to outward appearances, and that the primary criterion for classification is genuine adherence to religion, creed, and ethics.

Furthermore, these labels should be avoided if they are used to divide people or to judge them unjustly, especially in matters of ijtihad (independent reasoning). It is better to describe people with specific and clear descriptions such as: "observes prayers" or "recites the Quran," as these reflect the truth without the interference of personal opinion or malice.