A jelerősség rossz.

In Hungarian, the verb to be is often left out in the present tense, third person when you are linking a subject to a noun, adjective, or adverb.

So:

• A jelerősség rossz. = The signal strength is bad.

There is no spoken or written van here.

Compare:

• Én fáradt vagyok. = I am tired.
• Te fáradt vagy. = You are tired.
• Ő fáradt. = He/she is tired.

So in the third person singular, Hungarian often just uses:

• subject + adjective

That is exactly what is happening here.

A is the Hungarian definite article, meaning the.

So:

• a jelerősség = the signal strength

Hungarian has two forms of the definite article:

• a before most consonant-initial words
• az before vowel-initial words

For example:

• a ház = the house
• az autó = the car

Since jelerősség starts with a consonant sound, it takes a.

Hungarian often uses the definite article in places where English may or may not use one.

So A jelerősség rossz is perfectly natural, even if English might say either:

• The signal strength is bad
• Signal strength is bad

In Hungarian, using a here sounds normal and expected.

Jelerősség is a compound noun, which is very common in Hungarian.

It is made up of:

• jel = signal
• erősség = strength

So literally:

• jelerősség = signal-strength

Hungarian very often combines ideas into a single word where English uses two separate words.

Other examples:

• napszemüveg = sun + glasses = sunglasses
• vasútállomás = railway + station = train station

So the long word is completely normal.

A rough pronunciation guide is:

• yeh-leh-roe-shshayg

A few key points:

• j in Hungarian is pronounced like English y
• e is usually like e in bed, but shorter and cleaner
• ő is a long front rounded vowel, something like German ö but held longer
• s is pronounced like English sh
• sz is pronounced like English s
• g is always a hard g, like in go

So:

• je-le-rős-ség

Also, Hungarian stress is always on the first syllable:

• JE-lerősség

Yes. Rossz is a very common adjective meaning:

• bad
• poor
• wrong in some contexts

Here it means that the signal strength is poor or bad.

Examples:

• rossz idő = bad weather
• rossz válasz = wrong answer
• rossz minőség = bad quality

In your sentence, rossz describes the quality of the signal strength.

No. Hungarian adjectives do not agree in gender, because Hungarian has no grammatical gender like French or German.

Also, predicate adjectives in sentences like this usually do not change for singular vs. plural in the same way English learners might expect.

So:

• A jelerősség rossz. = The signal strength is bad.
• A kapcsolatok rosszak. = The connections are bad.

In plural, the adjective can take plural marking in this kind of sentence, but there is still no gender agreement to worry about.

The important thing for learners is:

• no masculine/feminine/neuter forms
• adjectives are much simpler than in many European languages

Yes, absolutely.

Both are possible:

• A jelerősség rossz.
• Rossz a jelerősség.

The difference is mainly about focus and information structure.

• A jelerősség rossz. = neutral, straightforward statement
• Rossz a jelerősség. = puts more emphasis on bad

That second version can sound a bit more like:

• The signal strength is bad
• The signal strength is poor

with the badness being highlighted.

Hungarian word order is flexible, but it is not random. It often shows what is being emphasized.

Often, yes.

While A jelerősség rossz is understandable and grammatically correct, in real-life situations Hungarian speakers may more naturally say:

• Gyenge a jelerősség. = The signal strength is weak.
• Gyenge a jel. = The signal is weak.
• Gyenge a térerő. = The reception/signal is weak.

Why?

Because for signal strength, weak is often more idiomatic than bad.

So:

• rossz = bad
• gyenge = weak

Both can work, but gyenge is often the more natural choice when talking specifically about signal strength.

These are related but not identical.

• jel = signal
• jelerősség = signal strength
• térerő = signal strength / reception, especially with phones and mobile networks

Examples:

• Nincs jel. = There is no signal.
• Gyenge a jel. = The signal is weak.
• Gyenge a térerő. = The reception is weak.
• A jelerősség rossz. = The signal strength is bad.

In everyday speech, térerő is very common for mobile reception.

Yes.

The structure is:

• A jelerősség = the subject
• rossz = the predicate adjective

So the sentence is basically:

• [The signal strength] [bad].

with the present-tense is understood but omitted, as Hungarian normally does in this kind of sentence.

You would say:

• A jelerősség nem rossz.

Here:

• nem = not

So:

• A jelerősség rossz. = The signal strength is bad.
• A jelerősség nem rossz. = The signal strength is not bad.

The negation word nem usually comes directly before the word or phrase being negated.

Yes, it can.

Jelerősség is a general term for signal strength, so it can be used in technical or everyday contexts such as:

• phone signal
• Wi‑Fi signal
• radio signal
• network signal

That said, in casual conversation, people may choose shorter or more context-specific wording, such as:

• Gyenge a wifi.
• Gyenge a jel.
• Gyenge a térerő.

So your sentence is valid, but depending on context, a Hungarian speaker might choose a different expression that sounds more natural in everyday speech.