But convection currents are ultimately at the mercy of temperature differences because these are what create pressure differences in the first place. The pressure difference between two locations is called a pressure gradient, and the force that actually moves air as wind is called the pressure gradient force.
oÂ·nus. n. 1. A difficult or disagreeable responsibility or necessity; a burden or obligation. 2. Responsibility for an error or fault; blame: Each side wants to avoid the onus of having started the disagreement. 3.
Definition of on for Students. 1  1 : in contact with and supported by Put the books on the table. 2  2 âused to indicate means of being carried He rode on a tractor. 3  3 âused to indicate the location of something Both bedrooms are on the top floor.  4 âused to indicate the focus of a certain action He went down on his stomach. She chewed on gum.