inefficient

Incapable is a synonym of inefficient.

As adjectives the difference between incapable and inefficient

is that incapable is not capable (of doing something); unable while inefficient is inefficient.

As a noun incapable

is (dated) one who is morally or mentally weak or inefficient; an imbecile; a simpleton.

As adjectives the difference between incompetent and inefficient

is that incompetent is unskilled, lacking normally expected degree of ability while inefficient is not efficient; not producing the effect intended or desired; inefficacious; as, inefficient means or measures.

As a noun incompetent

is a person who is incompetent.

As an adjective inefficient is

inefficient.

Unqualified is a related term of inefficient.

As adjectives the difference between unqualified and inefficient

is that unqualified is not qualified, ineligible, unfit for a position or task while inefficient is inefficient.

Unskilled is a related term of inefficient.

As adjectives the difference between unskilled and inefficient

is that unskilled is of a person or workforce: not having a skill or technical training while inefficient is inefficient.

As adjectives the difference between untrained and inefficient

is that untrained is lacking training, not having been instructed in something while inefficient is not efficient; not producing the effect intended or desired; inefficacious; as, inefficient means or measures.

As adjectives the difference between inefficient and inefficient

is that inefficient is inefficient while inefficient is inefficient.

Unfit is a related term of inefficient.

As adjectives the difference between unfit and inefficient

is that unfit is not fit; not having the correct requirements while inefficient is inefficient.

As a verb unfit

is to make unfit; to render unsuitable, spoil, disqualify.

As a noun underuse

is the act of using (something) less than expected.

As a verb underuse

is to use (something) less than expected.

As an adjective inefficient is

inefficient.