Жар стал сильнее.

Жар can mean heat, fever, or burning sensation, depending on context.

In a sentence like Жар стал сильнее, it often means:

• the heat became stronger
• the fever got worse
• the burning sensation intensified

A learner should also know that жар is not the same as жара:

• жар = heat, fever, intense heat
• жара = hot weather, heat outside

So жар is the better word for physical heat, fever, or an intense internal sensation.

Стал is the past tense of стать, which means to become.

So стал сильнее literally means:

• became stronger

In natural English, that may be translated as:

• got stronger
• became more intense
• got worse (if talking about fever)

This is a very common Russian pattern:

• стать лучше = to become better
• стать хуже = to become worse
• стать сильнее = to become stronger

Because стал agrees with the noun жар, which is masculine singular.

Russian past tense verbs change for gender and number:

• masculine: стал
• feminine: стала
• neuter: стало
• plural: стали

Since жар is masculine, the verb must be стал.

Сильнее is the comparative form of сильный (strong).

So:

• сильный = strong
• сильнее = stronger / more intense

In this sentence, сильнее means that the heat or fever increased in intensity.

Russian often uses this comparative form where English might use:

• stronger
• more intense
• worse

depending on the context.

Because this sentence uses a comparative idea: became stronger.

Compare:

• стал сильным = became strong
• стал сильнее = became stronger

These are different meanings.

Also, after стать, a normal adjective often appears in the instrumental case:

• Он стал сильным. = He became strong.

But the comparative form сильнее does not decline by case here. It stays сильнее.

So:

• сильным = full adjective, instrumental
• сильнее = comparative form, no case ending here

Yes. A comparative like сильнее usually implies stronger than before or stronger than it was.

Russian often leaves that comparison unstated if it is obvious from context.

So Жар стал сильнее naturally means:

• the fever became stronger than before
• the heat got more intense than earlier

If needed, Russian can make the comparison explicit:

• Жар стал сильнее, чем вчера. = The fever became stronger than yesterday.
• Жар стал сильнее, чем был раньше. = The heat became stronger than it was before.

Жар is in the nominative case because it is the subject of the sentence.

It is the thing that became stronger.

So the structure is:

• жар = subject
• стал = verb
• сильнее = comparative complement

This is a very normal Russian sentence pattern.

The difference is important:

• Жар стал сильнее = the fever/heat became stronger
• Жар был сильнее = the fever/heat was stronger

So:

стал focuses on a change

• something increased
• it was one way before, and then changed

был describes a state

• it was stronger at some time
• often compared with something else

For example:

• К вечеру жар стал сильнее. = By evening, the fever got stronger.
• Вчера жар был сильнее. = Yesterday, the fever was stronger.

Yes, Russian word order is flexible, but Жар стал сильнее is the most neutral and natural order.

Other orders are possible, but they sound more marked or emphatic. For example:

• Сильнее стал жар.

This could be used for emphasis or in a more literary style, but it is less neutral.

For a learner, the safest default is:

• subject + verb + complement
• Жар стал сильнее.

The stress is on the е:

• сильнЕе

A rough pronunciation guide is:

• zhar stal seel-NYE-ye

A few useful notes:

• ж sounds like the s in measure
• льн in сильнее is soft before the stressed vowel
• the ending -ее is pronounced clearly, not reduced to one sound

So the whole sentence is pronounced approximately:

• Жар стал сильнЕе.