Yardstick competition: regulatory pricing policy in which an average of the marginal costs of all competing firms is used as a standard of payment to induce the firm to engage in cost-cutting innovations. polityka konkurencji porównawczej

Yates' correction: adjustment made in the calculation of the chi-squared statistic in two-by-two tables that is often used in small samples; used in some other calculations too, but almost always in the case of small sample sizes. poprawka Yatesa

Years of healthy life (YHL): duration of an individual's life, as modified by the changes in health and well-being experienced over a life-time; cf. quality-adjusted life years, health-adjusted life years. lata życia w zdrowiu

Years of potential life lost: measure of the impact of premature mortality on a population, calculated as the sum of the differences between some predetermined minimum or desired life span and the age of death for individuals who died earlier than that predetermined age. potencjalne utracone lata życia

Yellow fever: dangerous infectious tropical disease caused by viruses transmitted by mosquitoes;symptoms include high fever with a slow pulse, muscle pain, backache, shivers, loss of appetite, jaundice, gastrointestinal haemorrhage. żółta febra

Yield: quantity of water that can be collected for a given use from surface or groundwater sources; may vary with the use proposed, with the plan of development, and also with economic considerations.