都是“全世界,世界各地”的意思. around the world中,around是介词“在…周围”+ the world宾语; all over the world 中,all 是副词“完全地”修饰over“遍及”这个介词 + the world做介词的宾语 across the world 中,across是介词“横穿” + the world做介词的宾语;
all over the world = around the world = throughout the world 全世界,世界各地 across the world意思是全世界,世界各地,横跨世界。 people celebrate the New Year hapilly across the world. 世界各地,人们欢度新年.