Branch - (noun)
The branch of a trade union is the base unit of a trade union organisation. It can be based around a workplace, a region, or the sector in which workers are employed.
Source: Own Definition
Example of Use: Each GMB branch (a major trade union in the UK) is usually made up of a number of workplaces in the local area. It is usually the first place that you go if you have a problem with your employer.