adverb · in fact; in reality; as a matter of fact

他表面上很镇定，实际上非常紧张。

noun, adverb, punctuation · as a matter of fact; in point of fact; in reality; actually

他表面上很冷静，实际上心里非常着急。

adverb · in practical application or operation

理论上可行，但实际上很难做到。