She is intelligent but her sisters are dull.
She is intelligent but her sisters dull.
Both sentences are correct. But the second sentence is missing "is" before dull. Can anyone explain this?
She is intelligent but her sisters dull.
The missing word 'are' after 'sisters' is an example of 'ellipsis', to be specific, 'gapping':
a situation in which words are left out of a sentence but the sentence can still be understood.
“I went to the mall on Monday, and she on Sunday.” (meaning “I went to the mall on Monday, and she went to the mall on Sunday.”)
There is a second, related meaning of 'ellipsis':
three dots in a printed text that show where one or more words have been intentionally left out.
"You went to the restaurant, and…?" (meaning "You went to the restaurant, and what happened?")