Length is defined as the distance between two points. This can be the length of an object, thickness of an object, breadth of an object, height of an object, distance between two places, etc. Length is a basic physical quantity. The standard unit of length is metre.

The mass of an object is defined as the amount of matter present in it. The SI unit of mass is kilogram. It is a basic physical quantity which can neither be created nor be destroyed. Examples where mass can be measured are all the objects in the nature which has a measurable quantity of matter in it.

Area is defined as the extent(amount) of surface(region) covered by an object. Area is a two-dimensional measurement. Some of the examples where we can measure area are a square, a triangle, a rectangle, a circle, cross-sectional area of a cylinder, etc.

A particular moment in a day is called an instance of time. In ancient times there was no time-measuring device. Our ancestors depended on many natural events to measure time. Later, time is measured using clocks, hour glass, digital clocks, sun dial, etc.