Contronymns are words that are their own antonymns.

transparent means nearly invisible (the clean window was transparent)
transparent means obvious (her feelings were transparent)

 variety means one type (this variety of apple is tart)
 variety means many types (there were a variety of apples available)

weather means withstand (this ship can weather any storm)
weather means wear away (this unsealed decking will weather over time)

Contronyms are words that are their own antonymns.

sanction means to approve (the governor will sanction the organization)
sanction means to penalize (the trade sanction prevented export)

screen means to show information (the movie will screen Thursday)
screen means to hide information from viewing (the warden will screen the mail)

seed means to plant an area with seed (seed the future lawn)
seed means to remove seeds from something (seed a tomato)

Contronyms are words that are their own antonymns.

out means visible (the stars are out early tonight)
out means invisible (the street lights are out in this part of town)

oversight means an error (the misspelling was an oversight)
oversight means care (he was given oversight of the child)

rent means to pay for the use of something (she needs to rent a car)
rent means to sell the use of something (the dealer will rent him a car)

Contronyms are words that are their own antonymns.

garnish means to add decoration (garnish with parsley)
garnish means to take away (money from a paycheck)

left means went away (left for school)
left means remaining (left behind)

off means non-operational (shut the light off)
off means operating (the alarm went off)

Contronyms are words that are their own antonymns.

clip means to attach (as with a paper clip)
clip means to detach (as the tip of a finger nail)

consult means to seek advice
consult means to advise

dust means to remove dust from something
dust means to add dust to something (as in dusting for prints)

 will is used to express intent or something scheduled

would is the past tense of will

will/would is a modal verb pair like can/could, may/might/must, shall/should

For a complete explanation of  will/would, visit Grammar-Quizzes.com.

may is used to express permission
May I come in? Yes, you may.

may is used to express something which is possible but not certain
He may be hiding a weapon.

may not is the proper negative form for may

might not are the proper negative form for might

might is the past tense of may
She might have done better if she had studied

might is used to express something which is unlikely
The boss might ride a tricycle around the office, but I doubt it.

might is better to use than may concerning doubt about something happening
We might not attend to the event.

For more information, visit Grammar Girl.

Can is used to express ability
He can lift the heavy suitcase onto the cart.

Can is used to express a possibility
There can be risks in any strenuous activity so take it easy.

Cannot is used to express belief
It cannot be midnight already.

Could is used to make requests
Could I have more dessert?

Could is the past tense of can.
Yesterday I could barely stand in the strong wind.

We gained our independence from Britain and now have different spellings for certain words. Why is this the case?

“The first answer is to blame Noah Webster, of Webster’s Dictionary fame. He believed it was important for America, a new and revolutionary nation, to assert its cultural independence from Britain through language. He wrote the first American spelling, grammar, and reading schoolbooks and the first American dictionary. He was also an ardent advocate of spelling reform, and thought words should be spelled more like they sound.”
For the rest of the explanation, visit Grammar Girl.

English uses the Latin alphabet of the Romans. However, this had no letter suitable for representing the phoneme /w/ which was used in Old English, though phonetically the sound represented by /v/ was quite close. In the 7th century scribes wrote uu for /w/; later they used the runic symbols known as wynn. European scribes had continued to write uu, and this usage returned to England with the Norman Conquest in 1066. Early printers sometimes used vv for lack of a w in their type. The name double-u recalls the former identity of u and v, which is also evident in a number of cognate words (flour/flower, guard/ward, suede/Swede, etc.). (Oxford Companion to the English Language)

From http://www.askoxford.com/asktheexperts/faq/aboutenglish/doubleu