Polite means showing regards for others in manners, speech, and behavior. Since you are a polite dinner guest, you thank the host for inviting you and, even though you think the chicken is not cooked to perfection, you tell her you are enjoying the meal.
The adjective polite comes from the mid-13th century Latin politus, which means "refined" or "elegant." Showing consideration for others, using tact, and observing social norms are the qualities of being polite. The opposite of polite is rude. Because the poet E.E. Cummings thought imagination is most important, he wrote, “Knowledge is a polite word for dead but not buried imagination.”