When person feels weak he/she need to do extra effort to perform everyday activities and feel exhausted or tired after little activity. The term weakness is used synonymously with tiredness or fatigue which is not correct. Weakness may be classified in two categories subjective or objective weakness.Subjective weakness is a condition when the person feels weak, but has no measurable loss of strength while in condition of objective weakness there occurs measurable loss of strength.

Weakness may also be generalized (total body weakness) or localized to a specific area, side of the body, limb, or muscle. Localized weakness is more notable because it may be followed by a stroke, exacerbation of multiple sclerosis, trauma to a motor nerve root or peripheral nerve, etc. General weakness can be felt due to number of conditions including metabolic, neurological, primary muscular diseases, and toxic disorders.