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

Unsatisfied vs Dissatisfied:

If you are unsatisfied with something, you are disappointed because you have not got what you hoped to get.
If you are dissatisfied with something, you are not contented or pleased with it.

Both words express a lack of satisfaction, “unsatisfied” is a more neutral term while “dissatisfied” has a stronger negative connotation.

‘un’ = 2 letters
‘dis’ = 3 letters (1 letter more, so stronger in negative emotion)