This is the 229th most frequent Czech word.
nejsou
"Nejsou" means "they are not" in English.
The word 'nejsou' functions as a negation for the plural subject 'knihy' in the sentence, stating where the books are not.
Tyto knihy nejsou na stole.
These books are not on the table.
Here, 'nejsou' is used with the plural subject 'oni' to negate their being at home.
Oni nejsou doma.
They are not at home.
In this sentence, 'nejsou' indicates negation for the plural subject 'obrázky,' describing their dissimilarity.