How can fain be used in a sentence?

The word "fain" is archaic and rarely used in modern English. It means "gladly" or "willingly". Here are some examples of how it could be used in a sentence:

* "He was fain to accept the offer, as it meant he could finally pursue his dream."

* "The weary traveler was fain to rest under the shade of the ancient oak."

* "Though she knew it was dangerous, she was fain to help her friend in need."

However, it's important to note that using "fain" in modern writing might sound overly formal or even affectatious. It's best reserved for specific situations where you want to evoke an older, more literary style.