Idioms are expressions that have a figurative meaning different from the literal meaning of the words. They're often culturally specific and can be tricky to understand if you're not familiar with the language.
Here are a few *potential* candidates from the book:
* "Living in a dream": This phrase is used figuratively throughout the book to describe the state of mind of those who have undergone the cure, essentially living in a blissful ignorance of love and its complexities. This phrase is not necessarily an idiom in the strictest sense, but it does have a figurative meaning.
* "Going off the deep end": While not explicitly stated, this phrase could be applied to Lena's journey as she starts questioning the cure and delves into forbidden territory. The "deep end" in this context represents the world of love and rebellion against the government's control.
* "To be in love": This phrase itself is not an idiom, but the book explores the concept of "love" in a very different context. It's not simply a feeling, but a dangerous, powerful force that the government tries to eradicate. This reinterpretation of the phrase could be considered figurative.
It's important to note that these are just possible interpretations. Ultimately, whether a phrase is considered an idiom is subjective and depends on how it's used in the specific context.