We use used to to talk about past habits or situations that were true before but are not true anymore. The structure is simple: subject + used to + base verb. For example, we say I used to play football to show that playing football was a regular activity in the past. In the negative form, we say I didn’t use to play football, and in questions, we say Did you use to play football? It’s important to remember that used to is only used for repeated actions or states in the past, not for something that happened once. For example, we say Nadia didn’t go to the premiere, not Nadia didn’t used to go to the premiere. In short, used to helps us describe habits or situations that have changed over time.