Definition

H-index

An author metric: h papers with at least h citations each. Balances productivity and impact, with well-known biases.

An h-index of 20 means twenty of your papers have twenty or more citations. It resists inflation by one blockbuster (unlike total citations) and by paper-count padding (unlike raw output) — which made it the default author metric almost overnight after Hirsch proposed it in 2005.

Its biases are equally established: it only grows, favoring seniority; it varies wildly across fields with different citation cultures; and it ignores author position and contribution. Compare within a field and career stage, or not at all.