業 business

The hedgehogs made a lot of yen in their tree business. They'd yell "GET YOUR trees here, cheap!"

overtime work ★★★★☆
残 (remain behind) + 業 (business) = 残業 (overtime work)

heavy industry ★★★☆☆
産 (childbirth, production of things) + 業 (business) = 産業 (heavy industry)

heavy industry, like 'the steel or construction industry.'

industry ★☆☆☆☆
工 (craft or industry) + 業 (business) = 工業 (industry)

the fishing industry ☆☆☆☆☆