Question

what is isotonic solution. give one example

Answer 1

Most isotonic solutions do not provide calories or free water. Examples of isotonic solutions are 0.9% sodium chloride, commonly called normal saline (NS), and lactated Ringer's (LR). Hypotonic solutions have an electrolyte content of less than 250 mEq/L and are administered to expand the intracellular space

Answer 2

This refers to two solutions  having the same osmotic pressure across a semipermeable membrane. This state allows for the free movement of water across the membrane without changing the concentration of solutes on either side. 
example :0.9% sodium chloride, commonly called normal saline..