This is the 1694th most frequent Japanese word.
鴻
"鴻" means "large bird," often referring to a swan or wild goose.
In this sentence, '鴻' is used as a noun to refer directly to the bird, emphasizing its characteristic as being large.
鴻は大きな鳥です。
A '鴻' is a large bird.
Here, '鴻' appears as the subject of the question, highlighting the act of visually encountering the bird.
鴻を見たことがありますか？
Have you ever seen a '鴻'?
In this usage, '鴻' takes on a metaphorical meaning, being imbued in literary context to represent an abstract concept like hope.