Combinations
The number of ways to pick a group of items from a larger set when order doesn't matter. The number of pairs from n items is n × (n - 1) ÷ 2, which grows roughly with the square of n.
In plain English
Three people make 3 pairs, ten make 45, a hundred make 4,950. Anything that depends on pairs (handshakes, communication lines, possible conflicts, comparisons) grows much faster than the number of items. That's why big teams need structure, and why testing many things at once creates so many chances for a fluke.
Uncle Gary explains
When a late project's team grew from 5 to 10 people, the possible pairs who might need to coordinate went from 10 to 45.
Why it matters for your money
40 stocks make 780 pairs whose relationships matter for risk. Adding holdings adds connections faster than it adds diversification.
Where we tested it
Related terms
All glossary terms. Educational content, not financial advice.