I like the word "Synergy" when used correctly. If a job takes one person 4 hours, but the same job takes two people one hour each, then that's Synergy. More often one encounters the situation where that job takes two people three hours each, so the overall timescales go down by throwing more people at it (finished in 3 hours rather than 4), but increasing the cost (6 man-hours vs 4).
Most of my stuff is beyond even that; it'll take me 4 hours, but if there's someone "helping", then it'll take us 8 hours each. Hours 2, 3 and 4 are me unpicking all the stuff that the other person got wrong, and hours 5-8 are the Fight, the A&E visit and the Court Case.