Be aware that calling someone a kafir may offend, as it implicates rejection of Islam. Be cautious when using terms like 'kafir' in diverse settings.
Pro Tip 2/3
Avoid in Dialogue
Unless discussing theology, avoid using 'kafir' in conversation to prevent discomfort. When talking to people of different faiths, 'kafir' should be avoided.
Pro Tip 3/3
Historical Context
Understand 'kafir' within historical disputes and theological debates among Muslims. Historically, 'kafir' was used in disagreements about Islamic faith.