Each nation has their own language, custom and culture. To have a
common voice, all nations in the world need have a common language and
English is such a language. Nowadays, English is very important because it has
become an effective medium and is used winden in many fields. Especially, in
the intergration process, English is a mean to communicate and exchange
information, culture, technology and science among countries. Hence, learning
English has become a great demand of most people. However, it is not easy work
because English is very variety and complex. English learners have to face up
with many difficulties such as vocabulary, pronunciation, grammar in which
vocabulary is the most difficult problem. In English, a new word is normally
created by adding prefix or suffix in preceed or after root word. Noun is the
same, a singular countable form plural noun by adding “-s, -es” suffix after
noun. It sometimes changes both form and even the meaning of root noun. This
is not easy problem for learners.