japanese help?

米国(beikoku)is America.
It is a short form of 亜米利加(A-me-ri-ka)/亜米利加合衆国(Amerika gasshu-koku)the united states of America.
We don't use the character 亜 in spite that it is the initial character because 亜 is usually used for Asia(亜細亜). So we took the second character,米 and it is naturally called with the character国, "beikoku".
And 国(koku)means country.

米国　pronounce "bei-koku."
米国 means U.S.A.

"ç±³" has several meaning, in this case, ç±³ (bei) is an abbreviation
of 亜米利加 (pronounced "America")　,and
国 (koku) means country.a nation etc.

米国 is a formal expression.

At the present day, Japanese people write アメリカ（also pronounced America) , アメリカ合衆国(合衆国 =the United States ) or 米国(bei koku), and rarely write 亜米利加 (= an oldish Japanese word imported from China (in19th century?)

*************************

Other meanings of "ç±³" :

1. rice:　e.g. 米飯食（pronounced "bei-han-syoku" ;the meaning of the word is rice diet）
2. meter : e.g 50米 (50m), 10平米（10 square meter）　

and so on.

Please note that although US is 米国, Japanese people don't associate rice or meter with USA. In other words, Japanese don't think that US is the rice country.

Please also refer Wiktionary.

http://en.wiktionary.org/wiki/%E7%B1%B3#Readings

It is pronounced "beikoku", and it means "the United States of America".

As for dictionaries you can use the on-line ones mentioned above, but I recommend the "Kanji Learner's Dictionary" by Jack Halpern. It is very easy to use, and has several look-up methods, including a very intuitive one for when you don't know the pronunciation.

http://japanese.about.com/

www.freedict.com