This is the 202nd most frequent Persian word.
زیر
"زیر" means "under" or "below" in English.
Here, "زیر" means "under" and indicates the spatial relationship of the book being below the table's surface.
کتاب زیر میز است.
The book is under the table.
In this sentence, "زیر" is metaphorically used to describe being in an intense situation caused by work.
او زیر فشار کار بود.
He/she was under work pressure.
"زیر" signifies a spatial relationship, here meaning "below" the text in the context of positioning on the page.