1) The sitcom "Friends" is known for its iconic Central Perk coffee shop, where the main characters often gather.

2) The development of artificial intelligence (AI) has led to advancements in areas such as machine learning, natural language processing, and computer vision.

3) The concept of political parties allows for organized groups to mobilize support, articulate policy positions, and compete for political power through elections and political campaigns.

4) The Mongol Empire, under the leadership of Genghis Khan, became the largest contiguous empire in history, spanning from Asia to Europe.