Unions can be Formed by any Group of Workers

Within a trade or profession

This includes building trades such as electricians, carpenters, and plumbers, who all have their own unions, as do engineers and other professionals.

Within a specific industry

This includes unions such as the United Mine Workers, International Ladies' Garment Workers' Union, or the United Automobile Workers.

The United Automobile Workers (UAW) represents skilled craft workers, assembly-line workers, and unskilled workers in all of the major American automobile companies; the UAW negotiates separate contracts on behalf of the workers at each of the auto companies.

Within a sector

Sector unions organize workers across businesses in a particular sector, such as fast-food. Recently, groups such as Fight for $15 are organizing fast-food and other sectors which don't “focus on a single franchise or even a single company but brings together workers from several fast-food chains."

Public sector unions

Public Sector Unions include government workers, faculty at community colleges and state universities, teachers and other employees of the local, state and federal governments.

Independent unions

A single workplace can decide to unionize, and remain unaffiliated with established unions. Most recently, the Amazon Labor Union formed at a single warehouse, JFK8.