If you are applying for a visa, green card, or other U.S. immigration benefit, you will no doubt be asked to submit various documents -- perhaps your birth certificate, marriage certificate, and so on. However, if the documents you are submitting are in a language other than English, you may need to have them translated. (The exception would be if you are dealing with a U.S consulate in your home country that specifically assures you that it accepts documents in the language of that country.)
If a translation is required, here is how to deal with this.
You will need to submit both:
A copy of the original document is needed to demonstrate that it's the real thing. Even if the immigration authorities can't read what it says, they need to see what it looks like, and compare it to their internal guidelines regarding what constitutes an acceptable document from your country. If, for example, it is missing the government stamps that the immigration officials are accustomed to seeing on such a certificate, it might be rejected.
A "word-for-word" translation is just what it sounds like: Not a summary, but an exact transcription of every word on the document, even if they seem irrelevant.
You do not necessarily need to spend money hiring a certified translator. Any trustworthy friend who is fluent in English and the language of the document and is not your close relative is allowed to do the job. That person should, after typing out the (word-for-word) translated text, add the following language at the bottom:
I certify that I am competent to translate from [the language of the document] to English and that the above [identify the document and to whom it pertains; for example, “Birth Certificate of Maritza Malakoff”] is a correct and true translation to the best of my knowledge and belief.
Signed: [translator’s full name]
If you prefer, however, you can hire a professional translator. That person should also add the same certification at the bottom of the translation.