Translation:I am John.
Seconding that, verbs are used at the end of most sentences, although they can appear in the middle of sentences too (e.g. as part of relative clauses).
Technically, you could include things like か as exceptions, but they're kind of verb modifiers and so still sort of part of the verb.
Other exceptions include: ください kudasai meaning "please".
だろう darou which has a few uses, including indicating a prediction/expectation, or making the sentence behave as a rhetorical question.
I can't think of any more off the top of my head which aren't simply different verb conjugations.
That's right. You can pronounce the 'u'. Whether you do or don't just indicates which region of Japan you are from or from whom you learned Japanese. It's akin to a "Southern drawl" in U.S.A. or to an Irish "Brogue" - both are completely acceptable English, it just gives the listener an idea of where you were born/raised.
The 'u' is there in misuteri and other words. They just don't say 'U' where you purse/round the lips, so you won't hear it as a long 'oo' sound (as in moon or do). Try saying u with your lips relaxed (not rounded).
At the end of sentences, where 'desu' is, it's usually not pronounced.
It is! But in japanese, they love to assume things with context already given. Here, we aren't given context explicitly, but we can kind of assume you're in a situation where you're introducing yourself to someone. Because it's just the two of you, it would be weird to say "you are John" or "some other person is John", so we can assume you're talking about yourself. If you were with another person, you might want to specify "私 は ジヨン です。" to not confuse the person with who you are introducing, but otherwise if there isn't a subject, and it makes sense (e.g. not asking a question), you can usually assume you're talking about yourself.
I am Japanese. 'わたしは、ジョンです' is correct. 'ジョンです' is ambiguous. We are omit the subject word often in conversation etc. Because there are other sentences or hint near the sentence.
But there is this sentence only here. And you are studying now. I think translation correct is important. And I use 'わたしは日本人です' usually.
I learned that aside from doing subject if understood, watashi wa and anata wa are rarely used. But in telling your nationality like in your example and when you want to contrast information, they are used. Ex. Konnichiwa, John desu. Watashi wa Amerikajin desu.
Isn't this correct?
It would be "Watashi no namae wa John desu." if we want to go to that length. "Watashi wa John desu." is probably more what you were thinking of.
Think of ジョンです。"John desu." as Duolingo's way of giving an organic example of language used if you were going round introducing 30 people. They wouldn't all 30 of them necessarily say "Hello, pleased to meet you, my name is John". They might just hear "What's your name?" and go with "It's John"
Please read the other comments before asking. This exact question had already been asked and answered at least twice in this discussion.
But to reiterate, yes, technically watashi wa john desu is the complete sentence, but watashi wa is regularly omitted when it's obvious what the subject is.
I agree with you Keith, but in my opinion, there will always be a "more natural" option in any given situation. However, I think even native speakers will have a very difficult time coming up with a consistent and logical reason/explanation for why one is more natural than the other.
As per my personal style, I tend to use full sentence when it is in formal situations, like in a speech. In casual situation, omitting obvious clauses are often more natural.
But it should not be an obligation, and every person has his own style of talking, so I just won't give recommendation.
One recommendation I can give is that, don't begin every sentence wih わたしは. Occationally adding わたしは when expressing own ideas is completely natural.
That's an alternative way to introduce yourself, not the only way. Which way is "normal" depends heavily on the social and conversational context of your introduction.
This has already been discussed at considerable length on this page; please try to read through the comments before posting.