What is null hypothesis? Why is a null hypothesis called null?

What will be an ideal response?

A null hypothesis is a statement that a population parameter equals a specific value. (Note: a null hypothesis never sets a range of values.) Letting P stand for probability, you can often state a null hypothesis in this way: H0: P = 0.5, which reads “the null hypothesis is that the probability of ‘producing’ heads is one-half.” After all, the very essence of a fair coin is that the probability of heads is one-half. In many research reports, the null hypothesis (H0) is that something (for example, a mean, a proportion) equals zero. Hence, the word null—because 0 represents no effect, such as no difference. But keep in mind that a null hypothesis can be an assertion that a population parameter equals any single number such as 0.5 or 100.