A to D
Averse and Adverse
Averse is an adjective meaning an opposition to something or a disinclination towards it, e.g. Due to her shyness she is averse to speaking in public. Adverse is also an adjective meaning hostile or having a negative effect, e.g. The race was cancelled due to adverse weather conditions.
Barbarous and Barbaric
Both are adjectives. Barbarous means cruel or behaviour that does not meet social standards, e.g. The way she spoke to him was barbarous. Barbaric is used to describe extreme violence or unpleasantness, e.g. Prisoners of war often experienced barbaric treatment.
Continuous and Continual
Continuous means something that does not cease, or without a pause, e.g. They worked continuously for eight hours. Continual is frequent, often in an annoying way, but with interruptions, e.g. Politicians continually twist the truth to gain votes.
Doubtful and Dubious
Doubtful means uncertain, e.g. It is doubtful that they will win the election. Dubious can also mean uncertain, but more often describes something fraudulent or untrue, e.g. The election result for many citizens is dubious to say the least.