Why is the final e dropped from base word believe to spell believable?

The final "e" is dropped from the base word "believe" to form "believable" because of a common spelling rule in English:

When adding a suffix beginning with a vowel to a word ending in a silent "e", drop the "e".

In this case, the suffix "-able" starts with a vowel ("a"). Since the "e" in "believe" is silent, it is dropped before adding the suffix.

This rule helps maintain consistency in pronunciation and spelling, ensuring that the added suffix is pronounced correctly.