"I do not know how to define him."
Translation:Je ne sais pas comment le définir.
Thank you n6zs, Sitesurf and chrystaenerys for answering my question about omitting "comment."
Sitesurf, as always, I am grateful that you are willing to share your language intuition and tell us how a construction or word sounds to an educated native speaker. How lucky we students of French are to have your generous help!
In French, "décrire" and "définir" are different as well.
What you find in a dictionary are definitions, not descriptions. For descriptions, you may use an encyclopedia.
If I am asked to define something, I will explain what it is, what it does, what it represents.
If I am asked to describe an object, I will use a few adjectives expressing what I see.
When it comes to people, there might be a bit of an overlap between what describes and what defines someone.
To describe a man, I can say he is tall and strong, dark-eyed and a few other things that will give you a full picture of what he is like.
To define a man, I can say he is top achiever or a shy dreamer or any other phrase that will give a full picture of who he is.
Your first sentence above: "In French, "décrire" and "définir" are different as well" was in reply to a comment that included this statement: "in English define and describe have completely different meanings." Your extended explication shows how they are different, not interchangeable. That being the case, I think only "définir" should be accepted to translate "define."
The French meanings of the two words are very close to the English meanings. In English, certainly, they are not interchangeable.
DianaM mentioned above that "describe" would be preferred in English and that "define" was less natural when it comes to people.
My earlier comments stressed the fact that describing someone and defining someone are different notions and both possible in French.
To keep Francophones and Anglophones happy, we therefore decided to accept both verbs from En to Fr, remembering that the original sentence was written in French with "le" that can be a male human being or a masculine thing.
The word taught here is "définir", so what I can do is to change the Best En translation to "define it", so that the reverse translation from En to French remains straight.
However, if I do so, this discussion thread will disappear.
This seems to be one of those rocky places in translation. "Describe/décrire" is fairly straightforward, and in many cases so is "define/définir". But when it comes to talking about people, we seem to veer apart on the second pair.
I am quite interested in Sitesurf's explication of the meaning of the two French words in this situation. If I am correctly understanding her, "décrire" refers to outward characteristics, while "définir" refers more to inward traits of personality.
Unfortunately, these two words diverge rather more in English. As I said, it would be odd to be asked to "define" some person. If someone asked me that, I'd be inclined to enquire into what exactly they wanted to know. But the word can apply to people - for example, I might observe that somebody's behaviour in a particular situation "really defines him, doesn't it?" That is, it really sums up his character. So there is a connection between the French and the English meanings, but it's a bit....stretched.