The difference between Fill-in and Relief

When used as nouns, fill-in means a temporary replacement for another, whereas relief means the removal of stress or discomfort.

Relief is also adjective with the meaning: characterized by surface inequalities.

check bellow for the other definitions of Fill-in and Relief

Relief as a noun:

The removal of stress or discomfort.

Examples:

"I sighed with relief when I found out that my daughter hadn't got lost, but was waiting for me at home."
Relief as a noun:

The feeling associated with the removal of stress or discomfort.
Relief as a noun:

The person who takes over a shift for another.

Examples:

"Officer Schmidt can finally go home because his relief has arrived."
Relief as a noun:

Aid or assistance offered in time of need.
Relief as a noun (legal):

Court-ordered compensation, aid, or protection, a redress.
Relief as a noun:

A lowering of a tax through special provisions; short for tax relief.

Relief as a noun:

A type of sculpture or other artwork in which shapes or figures protrude from a flat background.
Relief as a noun:

The apparent difference in elevation in the surface of a painting or drawing made noticeable by a variation in light or color.
Relief as a noun:

The difference of elevations on a surface.

Examples:

"the relief on that part of the Earth's surface"

Relief as an adjective (of a surface):

Characterized by surface inequalities.
Relief as an adjective:

Of or used in letterpress.