Identify the word that has been used incorrectly with respect to its specific approved word definition. Answer directly with the identified word and do not justify or explain your answer.

Sentence: The back support of the chair prevented fatigue.
Approved Definition: to an initial condition
Answer: back

Sentence: He exchanged his change for bills at the bank.
Approved Definition: that which occurs when something changes
Answer: change

Sentence: The elevator suddenly dropped a few inches before stopping.
Approved Definition: a small quantity of liquid in a spherical shape
Answer: drop

Sentence: The problem-solving task was exceptionally hard.
Approved Definition: not easy to cut, not easy to go into or through
Answer: hard

Sentence: The client's jerk behavior caused tension in the meeting.
Approved Definition: sudden movement
Answer: jerk

Sentence: {{sentence}}
Approved Definition: {{approved_definition}}
Answer: