na-adjective, noun
happiness; good fortune; blessing
Refers to a fortunate state or a piece of good luck. Often used in set phrases like 幸いなことに (fortunately) or 幸いです (I'm glad/happy).
See also: 幸いする (さいわいする)
ご無事で何よりの幸いです。
I'm most relieved that you're safe.
幸いなことに、大きな事故にはならなかった。
Fortunately, it didn't turn into a major accident.
adverb
Adverbial use, often at the beginning of a sentence or clause. Synonymous with 幸運にも.
幸い、雨はすぐにやんだ。
Fortunately, the rain soon stopped.