noun
key industry; basic industry
Refers to an industry that forms the backbone of a nation's economy, such as steel, energy, or transportation.
鉄鋼業は日本の基幹産業の一つです。
The steel industry is one of Japan's key industries.
主要産業 means 'major industry' in a broader sense, while 基幹産業 specifically implies a foundational or indispensable industry for the economy.
Compound of 基幹 (foundation, core) and 産業 (industry).