Which Keyword is Used to Start a Loop?

The keyword used to start a loop in most programming languages is "for".

The "for" loop is a fundamental control flow structure that allows you to execute a block of code repeatedly.

It is a powerful tool for iterating through collections of data, such as arrays or lists, and performing operations on each element.

Examples of "for" loops:

Python:
```
for i in range(5):
  print(i)
```
This loop will print the numbers 0, 1, 2, 3, and 4.
JavaScript:
```
for (let i = 0; i < 5; i++) {
  console.log(i);
}
```
This loop will print the numbers 0, 1, 2, 3, and 4.

Java:

for (int i = 0; i < 5; i++) {
  System.out.println(i);
}

This loop will print the numbers 0, 1, 2, 3, and 4.

While "for" is the most common, some programming languages also use other keywords for loops:

"while": This keyword is used for loops that continue executing as long as a certain condition is true.
"do-while": This keyword is similar to "while," but it guarantees that the loop body will execute at least once.

Remember that the specific syntax and keywords for loops can vary depending on the programming language you are using.