What is the function of 「や」 in this sentence?

Question

古池や 蛙飛び込む 水の音

This is a haiku by Matsuo Bashō. Is the や particle doing what it normally does, listing items?

Answer 1

The や indicates 詠嘆・感動 (exclamation/admiration). It's categorized as a 間投助詞 (interjectory particle) in デジタル大辞泉:

や 四 間助
３ 詠嘆・感動の意を表す。
「いで、あな幼なや」〈源・若紫〉
「夏草やつはものどもが夢の跡／芭蕉」〈奥の細道〉

And 明鏡国語辞典 categorizes it as a 終助詞 (final particle):

や (三)〘終助〙
❸ 詠嘆を表す。「これはすごいや」「ああ、恐ろしや、恐ろしや」「高く泳ぐや鯉のぼり〈鯉のぼり〉」◇俳句の切れ字もこれ。「古池や[蛙]{かはづ}飛び込む水の音〈芭蕉〉」

Answer 2

This や is a literary particle used to add emotion or exclamation. It's common in in haiku and waka. It works like O as in "O the ancient pond", or ... as in "The ancient pond...". Note that や has several roles. See jisho.org (the 4th definition) and the following question:

• What grammatical function is や performing here?