What's "so-called"? How do you use this expression?
Here, "so-called" means "referred to as". Usually, "so-called" introduces the name of something or someone, and implies that the speaker does not agree with the name. Ex: Carrots, apples, and eggs, so-called "healthy food", are a part of many people's diets. ("So-called" here refers to a title or name) Ex: Your so-called boyfriend didn't talk to you at the party. ("So-called" here implies that the speaker does not think the other person's "boyfriend" acts like a boyfriend should, so they are not deserving of the title "boyfriend")