The principles of translation
The first thing to remember is that translation is the transfer of meaning from one language to another. It is not the transfer of words from language to language. You must translate the meaning of what is being said, rather than do it word-for-word. This is because languages are not just different words. Different languages also have different grammar, different word orders, sometimes even words for which other languages do not have any equivalents. The English spoken by a scientist may have words which a simple farmer cannot even start to imagine. And the farmer is likely to have words for things the technologist never dreamed of.