उसका काम सफल हुआ।

उसका means his, her, or sometimes its, depending on context.

It comes from the pronoun वह (he / she / that). In this sentence, उसका काम means his work or her work.

Hindi often leaves gender to context, so उसका by itself does not tell you whether the person is male or female.

Because possessive words in Hindi agree with the thing possessed, not with the possessor.

Here, the possessed noun is काम (work / task), which is:

• masculine
• singular

So the correct possessive form is का:

• उसका काम = his/her work

Compare:

• उसकी किताब = his/her book (किताब is feminine)
• उसके दोस्त = his/her friends (दोस्त is plural)

This is one of the most important patterns in Hindi possession.

काम usually means work, task, job, or piece of work.

In this sentence, it most naturally means something like:

• a task
• a project
• an effort
• a piece of work someone was trying to do

So उसका काम सफल हुआ is not usually about employment. It is more about something he/she did turning out successfully.

Also, काम is a masculine noun, which matters for agreement.

सफल means successful.

It is an adjective. In this sentence, it is used predicatively, meaning it describes the state that the work reached:

• काम सफल हुआ
• literally: the work became successful

So Hindi is using an adjective + होना pattern.

Compare:

• वह खुश हुआ = he became happy
• योजना सफल हुई = the plan was successful / succeeded

हुआ is the past form of होना (to be / to happen / to become) agreeing with काम.

So सफल हुआ literally means:

• became successful
• turned out successful

In natural English, that may be translated as:

• His work was successful
• His work succeeded
• The task was accomplished successfully
  depending on context

Because काम is masculine singular, the form is हुआ.

If the noun were feminine singular, it would be हुई:

• उसकी योजना सफल हुई। = Her plan was successful.

Both are possible, but they are not exactly the same.

• उसका काम सफल हुआ = his/her work became / turned out successful
• उसका काम सफल था = his/her work was successful

The version with हुआ often emphasizes the result or outcome of something.

It suggests that after the work was done or after events unfolded, the result was success.

The version with था is more of a plain description of a past state.

So if you are talking about how something turned out, सफल हुआ is very natural.

Literally, the sentence talks about the work:

• उसका काम सफल हुआ = his/her work was successful

But in context, it can strongly imply that the person was successful in what they were doing.

Hindi often phrases things through the task, plan, or effort, rather than directly saying the person succeeded.

So the focus here is on the outcome of the work, not directly on the person.

If you wanted to say he succeeded, you might say:

• वह सफल हुआ। = He succeeded / became successful.
• वह कामयाब हुआ। = He succeeded.

Because this sentence is not structured as someone did something. It is structured as something became successful.

The grammatical subject here is काम:

• काम सफल हुआ = the work became successful

Since काम is not doing a transitive action on something else, there is no ने here.

A learner might expect something like:

• उसने काम किया = he/she did the work

That sentence has ने because the subject is the doer of a past transitive action.

But in उसका काम सफल हुआ, the idea is not he/she successfully did the work in that grammar pattern. It is his/her work turned out successful.

The verb हुआ agrees with काम, because काम is the subject here and it is:

• masculine
• singular

So we get:

• काम सफल हुआ

If the subject changed, the form would change too:

• योजना सफल हुई = the plan was successful (योजना is feminine singular)
• प्रयास सफल हुए = the efforts were successful (प्रयास is masculine plural)

So हुआ is not random; it matches the gender and number of the noun being described.

The normal and natural order is:

• उसका काम सफल हुआ।

This follows a common Hindi pattern:

• possessor + noun + adjective/result + verb

You should usually keep सफल हुआ together near the end.

Possible variations may happen for emphasis in poetry or speech, but for learners, the standard order is best.

So use:

• उसका काम सफल हुआ।

and avoid unnatural rearrangements such as:

• उसका सफल काम हुआ
• हुआ उसका काम सफल

unless you have a very special stylistic reason.

Yes. सफल and कामयाब are very close in meaning.

So you can say:

• उसका काम सफल हुआ।
• उसका काम कामयाब हुआ।

Both mean that the work succeeded or was successful.

A small nuance:

• सफल can sound a bit more formal or standard
• कामयाब is also very common and natural in everyday Hindi

In many contexts, either one works.

Here are some useful versions:

• उसका काम सफल नहीं हुआ। = His/Her work was not successful.
• उसका काम सफल हो गया। = His/Her work ended up being successful.
• उसका काम सफल होगा। = His/Her work will be successful.
• उसका काम सफल है। = His/Her work is successful.

A useful distinction:

• सफल हुआ = became / turned out successful
• सफल हो गया = ended up becoming successful, often with a stronger sense of completion or result
• सफल है = is successful

So for past result, सफल हुआ is a very natural choice.