Armrest (noun)

1. A support for the arm, typically one fixed to the side of a chair.
2. A horizontal bar or support to rest the arm upon.

Origin:

Late 19th century: from arm + rest.

Examples:

1. He adjusted the armrest on his chair to be more comfortable.
2. The armrests on the airplane seat were too low for him to rest comfortably.
3. The armrests on the couch are detachable.
4. The armrests on the wheelchair were padded for comfort.
5. He leaned on the armrest of the rocking chair while he read his book.