To express apology in Spanish, the most common phrase is “Lo siento,” which translates to “I’m sorry.” The more formal “Discúlpeme” can also be used. For deeper expressions, “Arrepentido” (regretful) or “Penoso” (shameful) can be used. Formal apologies use “usted” (you formal) while informal use “tú” (you informal). Cultural factors like acknowledging fault and seeking reconciliation are important. Effective apologies include sincerity, clarity, and appropriate language for the situation.