arduous

As a noun taxonomy

is the science or the technique used to make a classification.

As an adjective arduous is

needing or using up much energy; testing powers of endurance.

Ardorous is likely misspelled.

Ardorous has no English definition.

As an adjective arduous is

needing or using up much energy; testing powers of endurance.

In obsolete terms the difference between hard and arduous

is that hard is so as to raise difficulties while arduous is burning; ardent.

As adjectives the difference between hard and arduous

is that hard is having a severe property; presenting difficulty while arduous is needing or using up much energy; testing powers of endurance.

As an adverb hard

is with much force or effort.

As a noun hard

is a firm or paved beach or slope convenient for hauling vessels out of the water.

As adjectives the difference between arduous and toilsome

is that arduous is needing or using up much energy; testing powers of endurance while toilsome is requiring continuous physical effort; laborious.

As adjectives the difference between arduous and hardworking

is that arduous is needing or using up much energy; testing powers of endurance while hardworking is of a person, taking their work seriously and doing it well and rapidly.

As adjectives the difference between arduous and daunting

is that arduous is needing or using up much energy; testing powers of endurance while daunting is discouraging, inspiring fear.

As a verb daunting is

present participle of lang=en.