The hypothesis that is an alternative to the null hypothesis is represented as

The alternative hypothesis is symbolised as H-one or H1 and states that a real effect or difference exists.

H-zero or H0 denotes the null hypothesis, which asserts no effect or no relationship.

H-alt is not a standard statistical notation for the alternative hypothesis.

H-not-zero is an informal reading, not the accepted symbol used in testing.

The two hypotheses are mutually exclusive, and rejecting the null lends support to the alternative.

Some texts also write the alternative hypothesis as Ha, which carries the same meaning as H1.