illness

As an adjective painful

is causing pain or distress, either physical or mental.

As a noun illness is

(countable) an instance of a disease or poor health.

As nouns the difference between pain and illness

is that pain is while illness is (countable) an instance of a disease or poor health.

As an adverb pain

is towards, in/to the direction of.

As nouns the difference between disability and illness

is that disability is state of being disabled; deprivation or want of ability; absence of competent physical, intellectual, or moral power, means, fitness, and the like while illness is an instance of a disease or poor health.

As nouns the difference between complaint and illness

is that complaint is a grievance, problem, difficulty, or concern; the act of complaining while illness is (countable) an instance of a disease or poor health.

In countable terms the difference between illness and Weakness

is that illness is an instance of a disease or poor health while Weakness is a special fondness or desire.

In uncountable terms the difference between illness and Weakness

is that illness is a state of bad health or disease while Weakness is the condition of being weak.

As a noun illness is

(countable) an instance of a disease or poor health.

As nouns the difference between illness and allness

is that illness is (countable) an instance of a disease or poor health while allness is totality; completeness.

As nouns the difference between illness and problem

is that illness is (countable) an instance of a disease or poor health while problem is problem.

Sicknees is likely misspelled.

Sicknees has no English definition.

As a noun illness

is an instance of a disease or poor health.

As nouns the difference between taxonomy and illness

is that taxonomy is the science or the technique used to make a classification while illness is (countable) an instance of a disease or poor health.