My TOEFL students mix up these three words all the time!  Here’s what you need to know:

“Resident” = a person.  For example:

• “The residents of this city are really happy to live here.”
• “There were enough fireplaces for about 15 residents.”
• “Michael is a resident of Halifax.”

“Residence” = a place where someone lives (like a home). For example:

• “The houses in the Chaco Canyon were probably residences.”
• “There are over five thousand residences in downtown Seattle.”

“Residential” = an adjective with a meaning like “related to residences.”  For example:

• “They look like the residential buildings in New Mexico.”
• “This is a residential neighborhood.”

This one is tricky both for students and for teachers (to explain) but I see people misuse “decline” and “reduce” in their TOEFL essays all the time.  Here’s what you should note:

I can use “reduce” as a transitive verb to mean something like “make smaller”

• The whales reduced the population of sea otters.
• The hunters reduced the population of sea cows.
• To prevent a disaster in my apartment I reduced the amount of clutter.

In this case the subject of the sentence made the following things smaller:  the population of sea otters, the population of sea cows, the amount of clutter.

I can’t use “decline” as a transitive verb to mean “make smaller.”  I cannot say:

• The whales declined the population of sea otters.
• The hunters declined the population of sea otters.
• I declined the amount of clutter.

When talking about making something smaller, I can only use “decline” as an intransitive verb.  Like this:

• The population of sea otters declined.
• The population of sea cows declined.
• The amount of clutter declined.

It isn’t really relevant, but when I use “declined” as a transitive verb it means “refused” or “turned down.”  As in:

• I declined the job transfer. (I refused the job offer)

Students often mix up “few” and “a few” in their TOEFL essays and discussion responses.  Here’s what you should know:

“A few” means something like “some.”  You can’t use it when you are talking about a lot of something, but it does not necessarily mean “not many.”  Use it like this:

• “A few students passed the test” = some students passed the test (but not a lot of ideas)
• “I need a few ideas about how to negotiate a better contract” = I need some ideas about how to negotiate a better contract (but not a lot of ideas)
• “I saw a few people on my way to the store” = I saw a some people on my way to the store (but not a lot of people)

Just use “a few” when you are talking about “some” of something.  Don’t use it to emphasize that you are talking about “not many” of something.

“Few” means something like “not many”.  Use it when you want to emphasize that you are talking about “not many” of something.  Like this:

• “Few students passed the test” = not many students passed the test
• “I have few ideas about how to negotiate a better contract” = I don’t have many ideas about how to negotiate a better contract
• “I saw few people on my way to the store” = I didn’t see many people on my way to the store

Can you see the difference?  The correct wording depends on what you want to emphasize.