The pressure in a fluid is affected by what characteristics in that fluid?

1. The density of the fluid - if the fluid has more density it exerts more pressure.

2. The temperature value of the fluid - a fluid that has a higher temperature value is likely to exert more pressure than that with a lower temperature value since molecules vibrate faster in higher temperatures hence colliding with each other randomly consequently moving away from each much hence exerting more pressure.

3. The height of the fluid - keeping the density of the fluid constant; increasing the height of the fluid increases its pressure and reducing the height consequently reduces its pressure.

Gravity, acceleration or by force outside a closed container and by hydraulic mechanism and velocity of fluid.

Explanation:

Fluid pressure is defined as the force which is acted on unit area on an object which is present in the fluid or on the closed container's surface. This pressure can be changed by the acceleration, gravity, or forces  which are present outside a closed container.

Since there is no any definite shape of a fluid, the pressure which applies in these fluids observe in all directions. Fluid pressure can also be increased  by the  hydraulic mechanisms and velocity change of the fluid.

thermal energy is the answer