This is the 849th most frequent Hebrew word.
שאינו
"That is not" or "which is not."
שאינו - used here as "that does not" to negate a requirement associated with the preceding noun (profession).
הוא בחר במקצוע שאינו דורש ניסיון מוקדם.
He chose a profession that does not require prior experience.
שאינו - here it is used as "that is not," describing a temporary state of the object (car).
הרכב שאינו מתפקד כפי שצריך צריך תיקון מידי.
The car that is not functioning as it should requires immediate repair.
שאינו - meaning "that is not," it describes a characteristic (unclear) of the noun (text).