In math, LCD stands for "Least Common Denominator". It refers to the smallest number that can be a common denominator for a set of fractions. The concept of LCD is important when adding or subtracting fractions, as fractions need to have the same denominator to be added or subtracted. To find the LCD of a set of fractions, one can follow these steps:

1. Find the prime factors of each denominator.
2. Write the prime factors with their highest powers.
3. Multiply the prime factors with their highest powers to get the LCD.

For example, to find the LCD of 3/20 and 7/32, we can follow these steps:

1. The prime factors of 20 are 2 and 5. The prime factors of 32 are 2 and 2 and 2 and 2 and 2.
2. Write the prime factors with their highest powers: 20 = 2^2 * 5 and 32 = 2^5.
3. Multiply the prime factors with their highest powers to get the LCD: LCD = 2^5 * 5 = 160.

Therefore, the LCD of 3/20 and 7/32 is 160.