This is the 1115th most frequent Japanese word.
いかが
"いかが" means "how" or "how about" in a polite and formal context.
Here, 'いかが' is used to politely ask or suggest if the person would like to have some cake.
このケーキはおいしいですね。おひとついかがですか？
This cake is delicious, isn't it? How about having one?
In this sentence, 'いかが' is used to inquire about the person's experience or opinion in a polite way.
最近の旅行はいかがでしたか？
How was your recent trip?
This question uses 'いかが' to ask someone’s opinion or evaluation of the book’s contents.