If you are thinking of people working in an organization, then the plural is staff .The word is an uncountable noun.
In most universities, for example, we have teaching staff and administrative staff. Like the nouns jury, government, etc. the word staff can be followed by either a singular or a plural verb.
Here are a few examples.
• The staff is of the opinion that we should go on strike.
• The staff were excellent.
• The staff at St. Mary's Hospital have rejected the new pay scale.
The word is normally not used to refer to a single individual. If you wish to refer to a single person, then you could say staff member, staff person, etc. Some people use the word staffer, not everyone, however, accepts this word.