cog — A cog is a wheel with square or triangular teeth around the edge, which is used in a machine to turn another wheel or part.
part — a portion or division of a whole that is separate or distinct; piece, fragment, fraction, or section; constituent: the rear part of the house; to glue the two parts together.
disorder — lack of order or regular arrangement; confusion: Your room is in utter disorder.
inability — lack of ability; lack of power, capacity, or means: his inability to make decisions.
incompetence — the quality or condition of being incompetent; lack of ability.
lack — something missing or needed: After he left, they really felt the lack.
ignorance — the state or fact of being ignorant; lack of knowledge, learning, information, etc.
impotence — the condition or quality of being impotent; weakness.
idleness — the quality, state, or condition of being lazy, inactive, or idle: His lack of interest in the larger world and his consummate idleness were the causes of their dreadful divorce.