Definition:
a multitude is a large group of people or things, usually too many to count. It is usually used when referring to diverse groups, such as a collective gathering of nations or a wide array of opinions. Usage rules dictate that a multitude is always a plural noun, as it implies a collection of multiple items.
Examples:
1.The multitude of student organizations on campus provides unlimited possibilities for involvement.
2.The multitude of circumstances we are facing are precarious, at best.
3.The multitude of color and texture in this artwork is truly mesmerizing.
Tip:
be careful not to confuse this word with 'multiple' which refers to a set of two or more elements without implying a large number.