Allegiance is loyalty you owe, or choose to give, to a leader, a country, a belief, a team, or a cause. It is heavier than 'I like them': it says whose side you are on when it costs something. You swear, pledge, owe, or shift allegiance. Countries talk of allegiance to the flag; fans, a little loosely, of allegiance to a club. Fairly formal, except in set phrases like pledge allegiance. Though actually, the old core is feudal: a servant's bond to a lord, not a warm feeling of friendship. Today's word still carries that 'I am bound to you' taste, even when the lord is a republic or a brand.

效忠；忠誠（對國家、領袖、信念、團體）。美式「pledge allegiance」是效忠宣誓。