headcount

head +‎ count

headcount (plural headcounts)

1. The act of counting how many people are present in a group.
   • 2023 January 11, Stephen Roberts, “Bradshaw's Britain: castles and cathedrals”, in RAIL, number 974, page 56:

     Population 39,693 (just north of 115,000 today), Cheltenham has been overtaken by Gloucester in terms of headcount.

2. The number of people present in a group or employed by a company.
   • 2023 March 8, “Network News: More than 200 BTP vacancies”, in RAIL, number 978, page 12:

     The last headcount data for BTP is from December 2022, when the number of BTP officers was 3,183, up from 3,175 in April 2022.

3. More generally, a consideration of a company's appropriate staffing level based on some larger context. (Generally used adjectivally.)

   Due to economic difficulties, the company will be making headcount adjustments.

4. By extension, one slot in a workgroup, filled or to be filled by one person.

   I've convinced management to give us one more headcount, to take some work off the rest of us.

The two-word spelling head count refers neutrally to simple counts. The one-word spelling headcount tends to have a business jargon feel to it, especially when used adjectivally in phrases such as "headcount reduction", or in the extrapolated case where it refers to one person or one job opening.