billion – n. the number 1,000,000,000 : one thousand million
trillion – n. the number 1,000,000,000,000 : one thousand billion
effective – adj. producing a result that is wanted : having an intended effect
afford – v. to be able to pay for something
advance – v. to move forward
displace – v. to take the job or position of (someone or something
alternative – n. something that can be chosen instead of something else