In mathematics, the letter "n" can be used as a variable or unknown, representing any integer. Usually used to represent unknown quantities and unknown values of natural numbers, integers or positive integers.

"n" can also mean the nth element in the sequence, such as the nth item in the sequence.

In calculation, "n" is also often used to indicate the scale or size of a parameter or problem. For example, "n" can represent the input scale of an algorithm or the size of a problem.

In a word, "n" is a variable commonly used in mathematics and calculation to represent unknowns, parameters or the scale of problems, and its specific meaning usually depends on the context.