Which literary term is used in the following sentence: polite reciprocal curiosity out of a wan, charming, discontented face. It occurred to me that I had seen her, or a picture of her, somewhere before.

allusion

The literary term used in the given sentence is "reciprocal."

To identify the literary term in a sentence, you can follow these steps:

1. Read the entire sentence carefully to understand its meaning.
2. Pay attention to any words or phrases that seem significant or stand out.
3. Determine if any of these words or phrases are related to literary techniques or devices.
4. Analyze the context of the sentence and connect it to the most appropriate literary term.

In this sentence, the word "reciprocal" indicates a mutual or shared feeling. It suggests that there is a polite and mutual curiosity between the speaker and the person with the "wan, charming, discontented face." The word "reciprocal" emphasizes a sense of mutual interest, which is the literary term being used in this sentence.