Able: ability in general
Capable: ability in a special activity

Accede: consent
Exceed: surpass

Access: entrance
Excess: more than enough

Adapt: to fit one thing to another
Adept: skillful
Adopt: to take up

Advice: noun
Advise: verb

Aeroplane: plane, aircraft run by engine, has wings
Airship: dirigible balloon, aerostat or lighter-than-air aircraft, has no wing

Affect: attack, infect
Effect: accomplish, result

Afflict: trouble
Inflict: impose

Allusion: reference to
Illusion: deception

Altar: a place for offerings
Alter: change

Alteration: change
Altercation: quarrel

Alternate: coming by turns
Alternative: a choice between two things

Ambiguous: dual meaning, both are unclear
Equivocal: dual meaning, but, one is clear which is to misinterpret people

Amend: make or become better
Emend: take out mistakes from

Amiable: good-tempered, kind-hearted
Amicable: in a friendly way

Antic: odd
Antique: old-fashioned

Apposite: suitable
Opposite: contrary

Appraise: to assess, to form a decision about
Apprise: inform

Arab: the race
Arabic: language or literature
Arabian: belongs to the nation

Artful: clever, crafty.
Artificial: manufactured, unnatural

Artist: skilled in fine arts (music, sculpture, poetry, etc.)
Artisan: skilled in mechanic arts (carpentry, etc.)
Artiste: professional singer or dancer (male or female)

Ascent: going up
Assent: agreement

Assay: attempt
Essay: article, composition

Astonished: owing to beyond comprehension
Surprised: owing to unexpected

Authentic: the given data is true, factual, accurate
Genuine: one who provided the data is not fake

Avenge: take counter-retaliation against someone for others
Revenge: take counter-retaliation against someone for oneself
Vengeance: counter-retaliation in general

Avocation: regular customary occupation
Vocation: subsidiary occupation mainly for pleasure