A few commonly confused words

Part the first of what will probably be several posts.  Remember, the English language is messy.

affect/effect:  The simple answer is affect is a verb and effect is a noun. To keep them straight, watch your pronunciation and eventually you'll hear them correctly in your head. But when you're Word Nerdy like me, there's not a simple answer.  Stop reading if the simple answer is enough for you.  Effect, however, can also be used as a verb meaning "to put into effect" such as:  "In order to effect a change in civil rights laws, the people of a nation must overcome fears and prejudices."

uninterested/disinterested:  These had opposite meanings until sometime in the 19th century, but now the preferred use of uninterested is to show apathy or indifference, as in "She didn't like mystery novels and so was uninterested in attending the launch party for Vic Masters's latest Ace Gumshoe novel." Disinterested means unbiased, as in "It will be difficult to find a disinterested group of jurors in Crowley County because of the viciousness of the defendant's alleged crime."  You don't want a sports referee to be uninterested in the game, but you do want him or her to be disinterested in the outcome. Several online dictionaries say the two are synonymous and interchangeable because contextual use will make the intent obvious, but this Word Nerd prefers the distinction left intact.

lie/lay:  I get crap from people all the time about being something of a terminology nut, but the difference between these two is simple if you know the difference between a transitive verb and an intransitive one, and it becomes a sort of shorthand any time similar verbs show up.  Lie is intransitive, meaning it doesn't require a direct object.  "I need to lie down and try to get rid of my headache before company comes over tonight."  But:  "Lay the book on the table" because lay is transitive, meaning it takes a direct object.  In other words, "lie" is what you do, "lay" is what you do to something else.  Usually at this point, my ninth-grade English students will either snicker or one of the bolder spirits in the classroom will pipe up with, "or what is done to you." Or they'll ask, "so, 'getting laid" is proper usage because there's an object?" "Yes," I reply, "and this conversation never happened."

Simple past tense of lie is lay, as in "The shoes lay all winter under the snow, and were ruined by the time we found them in March."
Past participle is lain.  As with all participles, it requires an auxiliary verb:  "The book had lain on the shelf untouched for more than ten years."

Simple past tense of lay is laid, as in "He laid the flowers on the table and went to the pantry to look for a vase."
And its past participle is laid as well:  "She had laid her book on her nightstand and turned out the light when the phone rang.
Direct objects of both verbs are in yellow.

To clear your palate, enjoy a quote from Terry Pratchett:
"A European says, 'I can't understand this, what's wrong with me?' An American says, 'I can't understand this, what's wrong with him?'"