Viscosity of water/liquid is expressed in KN-s/m2. Let's break down the answer into headings and bullet points for better understanding:

Viscosity:
Viscosity is defined as the measure of a fluid's resistance to flow. It is a property of the fluid, and it varies with temperature, pressure, and composition.

Units of Viscosity:
Viscosity is expressed in different units depending upon the system of units used. The SI unit of viscosity is Pascal-second (Pa·s). Other commonly used units are:

- Poise (P) or centipoise (cP)
- Stokes (St)
- Reynolds (Re)
- Saybolt Universal Seconds (SUS)

However, in civil engineering, viscosity is often expressed in kilonewton-seconds per square meter (KN-s/m2). This unit is equivalent to Pa·s, which is the SI unit of viscosity.

Importance of Viscosity:
Viscosity plays a crucial role in various fields of engineering, such as:

- In civil engineering, viscosity is important in the design of hydraulic structures, such as dams, canals, and culverts.
- In chemical engineering, viscosity is essential in the design of pipelines, pumps, and heat exchangers.
- In mechanical engineering, viscosity is significant in the design of lubrication systems, such as engines, gears, and bearings.

Conclusion:
Viscosity is an essential property of fluids, and it is expressed in different units depending upon the system of units used. In civil engineering, viscosity is often expressed in KN-s/m2, which is equivalent to Pa·s, the SI unit of viscosity. Understanding viscosity is crucial in various fields of engineering, as it affects the design and performance of different systems.