I am often asked to translate a single sentence (or even a lone word). That, however, is unrealistic at best, and often impossible. The best you could do is giving a dictionary equivalent for each word and massage the grammar so it meant something. There is, however, a great chance that it won’t mean what it did before it was “translated”. Depending on the language, there is often information needed for the translation that is not in the sentence.
Every language has its own grammar and rules. When two people are communicating in that language, there are relatively few misunderstandings as both people know what the conversation is about, and understand the nuance of the words being used. However, when you are faced with just a small part of a conversation, it is often impossible to translate it accurately and naturally without extra information.
For example, in Japanese, there are two main words used to mean “father”: one indicates that it is your own father, and the other that it is not. There is, however, no other word necessary to indicate whose father when both parties to the conversation already know that fact. Also, there is no distinction between singular and plural nouns.
So, the following two sentences could result in the same Japanese.
（お父さんは犬の散歩をしている。）
● His father is walking the dog.
● Your father is walking the dogs.
Without asking questions and finding out whose father and how many dogs, it is impossible to correctly translate even this simple sentence.
A similar situation can arise when translating from English or Chinese into Japanese. For example, the simple sentence, “I will also go to Tokyo.” has two meanings. Without knowing whether there is another person or another place involved, it is impossible to know what the “also” refers to. In Japanese, however, the position of the “also” in the sentence makes it clear, and you therefore have two sentences.
The opposite is also a problem as both the Japanese sentences would often be translated into the same English or Chinese, leaving the reader wondering what was really being meant.
When translating, it is important to know the background, understand what information is really meant to be conveyed with the sentence, and then render it into the other language.
Translate the meaning, not the words!
