主な

1. Origins, structure, and basic meaning

• Structure: 主な (おもな) is a fixed attributive expression marking the principal item among several.
• Basic usage: Agriculture is a town's main industry; three main opinions from a meeting are summarized.

2. Common pitfalls and similar expressions

• Central local industry and principal discussion points
  • It directly modifies 産業 and 意見 and is not used sentence-finally as 主だ. Keep it distinct from an adverb meaning mostly.