Even though you know the difference in meaning between, say, it’s and its, its not uncommon to type the wrong one (okay, I did that on purpose). Then again, even good writers (and good typists) mix up words that are spelled differently and have different meanings but sound the same – that is, homonyms. I suspect that’s because they’re not really, really, really sure which one is right. Everyone has their particular bugaboo – mine is effect/affect; I am constitutionally incapable of using either without confirming I’m using the right word – and it’s worth noting yours and taking extra care when necessary.
I see these pretty regularly:
ad / add
An ad is short for advertisement (one d in each), while add is related to addition (a double d in each). The ad for chartreuse Christian Louboutin peep-toe pumps made her want to add them to her collection.
aid / aide
Aid is a verb and means to help or assist, while an aide is a helper or assistant. My aide aided in my indictment.
assent / ascent
To assent is to say yes; while to ascent refers to the act of climbing something. Anik assented to the ascent up Sacré Cœur.
born / borne
To be born is to be brought into existence, while borne is the past tense of bear, or to bring about. Right after Blanche was born, she contracted a water-borne illness.
cash / cache
Cash is what I never have enough of, while a cache is a secret store of something. Barney found a cache of $1,000 cash.
cite / sight / site
To cite is to refer to, while a sight is something you see and a site is somewhere you visit. The online site cited the sights of Venice.
counsel / council
To give counsel is to provide advice, while a council is a group of folks in charge. The council of elders counseled me to stop all my damn bellyaching.
discreet / discrete
Something discreet is confidential, while something discrete is distinct from other things. Penelope's discrete office affairs were mercifully discreet.
lesson / lessen
A lesson is something you learn or the time you take learning, while to lessen is to remove or reduce. Cristobel lessened his boorishness with a lesson in manners.
peak / peek / pique
A mountaintop is a peak, a quick look is a peek, and a hurt ego is a pique. Martha had a pique when she took a quick peek at Mt. McKinley’s peak and realized Stewart had beaten her there.
shear / sheer
A shear is a large tool for cutting, while sheer is either very thin and light transmitting or in a complete manner. Mr. Kenneth’s talent with a pair of shears was a sheer delight to see.