Japanese has a complex system of honorifics. This can be a wonderful thing when used correctly, but lead to absolute confusion when misused. One example of this is the word “wife”. There are a number of ways of referring to your own wife, with the most common probably being tsuma (妻), and another way of referring to somebody else’s wife which is okusan (奥さん).
Even with the latter, okusan, it is unclear whose wife is being talked about without the relevant context or background to the discussion, but it is clear that it is not the wife of the person doing the talking.
Although when referring to your own wife, you should use the word tsuma, recently it is becoming more common to incorrectly use the honorific form, okusan. So, more and more people are saying things about “my okusan” when referring to their wife. Even though this is technically incorrect, there is no confusion due to the fact that they include the “my”. However, it becomes a problem when this “my” is omitted, and that is also something that is being heard more and more recently.
So, when you hear somebody say that they are “going to dinner with okusan”; the immediate response should be to ask whose wife they are talking about. It is more than likely that it is just a mistaken use of the honorific, and they mean that they are going out to eat with their own wife, but there is no way to be sure without hearing the entire conversation.
When this sentence is given to a translator or interpreter without the relevant context to know whose wife is really being talked about, you are left with choosing between translating it as the person’s own wife (that is, assuming they are using the language incorrectly), or translating it as somebody else’s wife (which necessitates you asking them whose wife it is). More often than not, without the necessary context, you will have to confirm if it is the person’s own wife and get the necessary modifier (my, his, John’s, etc.) for the noun (wife). This can be embarrassing as it means that you are making it clear that the person is either using incorrect Japanese or going out to dinner with somebody else’s wife. Either way, the information is necessary to render a complete English sentence.
This emphasizes two important things about preparing a sentence for a translator. First is that you must ensure the translator has enough information (context, background, etc.) to fully understand what is being meant (not just said!), and second is that you must use your own language correctly.
In this example, assuming it was an innocent dinner with his own wife, it would have been much simpler to have said “I’m going to dinner with tsuma” and not “I’m going to dinner with okusan.”