**Union** of two given sets is the smallest set which contains all the elements of both the sets. Union of two given sets A and B is a set which consists of all the elements of A and all the elements of B such that no element is repeated.

The symbol for denoting union of sets is **‘U’****Examples:**

Input:Let set A = {2, 4, 5, 6} and set B = {4, 6, 7, 8} Output: {2, 4, 5, 6, 7, 8} Explanation: Taking every element of both the sets A and B, without repeating any element, we get a new set = {2, 4, 5, 6, 7, 8}.This new set contains all the elements of set A and all the elements of set B with no repetition of elements and is named as union of set A and B.

**Syntax:**

set1.union(set2, set3, set4….)

In parameters, any number of sets can be given

**Return value:**

The union() function returns a set, which has the union of all sets(set1, set2, set3…) with set1.

It returns a copy of set1 only if no parameter is passed.

Below is the Python3 implementation of the above approach:

`# Python3 program for union() function` ` ` `set1 ` `=` `{` `2` `, ` `4` `, ` `5` `, ` `6` `} ` `set2 ` `=` `{` `4` `, ` `6` `, ` `7` `, ` `8` `} ` `set3 ` `=` `{` `7` `, ` `8` `, ` `9` `, ` `10` `}` ` ` `# union of two sets` `print` `(` `"set1 U set2 : "` `, set1.union(set2))` ` ` `# union of three sets` `print` `(` `"set1 U set2 U set3 :"` `, set1.union(set2, set3))` |

**Output:**

set1 U set2 : {2, 4, 5, 6, 7, 8} set1 U set2 U set3 : {2, 4, 5, 6, 7, 8, 9, 10}

**Practical applications**:

In most of the probability problems, the concept of union of sets is needed.

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