> How do you define full employment? The unemployment rate in the USA is currently 3.8%.

3.8% is near historic lows.

More importantly: "full employment" doesn't mean unemployment is literally 0% - in fact, an unemployment rate of 0% would be actively bad, because it indicates that people are unable to leave their jobs (even temporarily) to seek better opportunities or life changes - usually because inflation is too high.

There's no strict definition, but an unemployment rate <4% almost certainly corresponds to full employment, as frictional unemployment can be expected to be ~4%.

BLS defines full employment as an economy in which the unemployment rate equals the nonaccelerating inflation rate of unemployment (NAIRU), no cyclical unemployment exists, and GDP is at its potential. [1]

[1] https://www.bls.gov/opub/mlr/2017/article/full-employment-an...