1) ADVERSE/AVERSE
The word “adverse” turns up most frequently in the phrase “adverse circumstances,” meaning difficult circumstances, circumstances which act as an adversary; but people often confuse this word with “averse,” a much rarer word, meaning having a strong feeling against, or aversion toward.
2) ADVICE/ADVISE
“Advice” is the noun, “advise” the verb. When Ann Landers advises people, she gives them advice.
3) ADVISER/ADVISOR
“Adviser” and “advisor” are equally fine spellings. There is no distinction between them.
4) AESTHETIC/ASCETIC
People often encounter these two words first in college, and may confuse one with the other although they have almost opposite connotations. “Aesthetic” (also spelled “esthetic”) has to do with beauty, whereas “ascetic” has to do with avoiding pleasure, including presumably the pleasure of looking at beautiful things.
St. Francis had an ascetic attitude toward life, whereas Oscar Wilde had an esthetic attitude toward life.
5) AFFECT/EFFECT
There are four distinct words here. When “affect” is accented on the final syllable (a-FECT), it is a verb meaning “have an influence on”: “The million-dollar donation from the industrialist did not affect my vote against the Clean Air Act.” A much rarer meaning is indicated when the word is accented on the first syllable (AFF-ect), meaning “emotion.” In this case the word is used mostly by psychiatrists and social scientists— people who normally know how to spell it. The real problem arises when people confuse the first spelling with the second: “effect.” This too can be two different words. The more common one is a noun: “When I left the stove on, the effect was that the house
filled with smoke.” When you affect a situation, you have an effect on it. The less common is a verb meaning “to create“: “I’m trying to effect a change in the way we purchase widgets.” No wonder people are confused. Note especially that the proper expression is not “take affect” but “take effect”— become effective. Hey, nobody ever said English was logical: just memorize it and get on with your life.