Some common synonyms of empty are blank, vacant, vacuous, and void. While all these words mean "lacking contents which could or should be present," empty suggests a complete absence of contents.

// an empty bucket

The words vacant and empty are synonyms, but do differ in nuance. Specifically, vacant suggests an absence of appropriate contents or occupants.

// a vacant apartment

Although the words vacuous and empty have much in common, vacuous suggests the emptiness of a vacuum and especially the lack of intelligence or significance.

// a vacuous facial expression