تجميد البطاقة ضروري.

Because Arabic often uses a nominal sentence in the present tense, with no separate word for is/are.

So:

تجميد البطاقة ضروري
literally = Freezing the card necessary

Natural English adds is: Freezing the card is necessary.

If you wanted past or future, Arabic would usually add a verb then.

تجميد is a verbal noun (also called a maṣdar) from the verb جمّد = to freeze.

In this kind of context, it usually means:

• freezing
• blocking
• suspending
• putting on hold

So with البطاقة it usually means something like:

• freezing the card
• blocking the card
• temporarily disabling the card

It does not usually mean physically putting a card in ice. In banking or service language, it means an administrative freeze.

Because the verbal noun تجميد can take its object directly, much like the verb itself.

Compare:

• جمّد البطاقة = He froze the card
• تجميد البطاقة = freezing the card

So البطاقة is the thing being frozen. Arabic does not need a preposition like of here, even though English often uses one in translation:

• freezing the card
• the freezing of the card

Both ideas are covered by تجميد البطاقة.

البطاقة is a definite noun: the card.

But ضروري here is the predicate of the sentence, and in Arabic the predicate usually does not take الـ in this kind of structure.

So:

• البطاقة = the card
• ضروري = necessary

This is normal Arabic sentence structure.
Adding الـ to ضروري here would sound wrong for this meaning.

Because ضروري is describing تجميد, not البطاقة.

The subject of the sentence is really:

تجميد البطاقة = freezing the card

The head of that phrase is تجميد, and تجميد is grammatically masculine.

So the logic is:

• تجميد = masculine noun
• therefore ضروري stays masculine

Also, in colloquial Arabic, ضروري is often used quite freely as a predicate without much noticeable agreement in everyday speech.

It is understandable, but it sounds a bit formal or written, closer to Standard Arabic style.

A more everyday Levantine way to say this would often be:

• ضروري نجمّد البطاقة = We need to freeze the card / It’s necessary to freeze the card
• لازم نجمّد البطاقة = We have to freeze the card

So the original sentence is not wrong, but it sounds more like formal service language, official writing, or a notice.

A common Levantine-style pronunciation would be:

tajmīd il-biṭā'a ḍarūrī

Some notes:

• تجميد = tajmīd
• ال is often pronounced il- or el-
• بطاقة is often pronounced with a glottal stop for ق, so biṭā'a
• ضروري = ḍarūrī

So you may hear something close to:

tajmīd il-biṭā'a ḍarūrī

In fast speech, the article may sound lighter: tajmīd l-biṭā'a ḍarūrī

تجميد البطاقة is a very normal formal way to express the idea as a noun phrase.

But in spoken Levantine, people often prefer a verb phrase instead of this kind of abstract noun. For example:

• نجمّد البطاقة = we freeze the card
• لازم نجمّد البطاقة = we need to freeze the card
• ضروري نجمّد البطاقة = it’s necessary to freeze the card

So:

• تجميد البطاقة ضروري = more formal, noun-based
• ضروري نجمّد البطاقة = more conversational

Yes. That is a very natural English rendering.

Arabic often expresses that idea with a noun phrase plus an adjective:

تجميد البطاقة ضروري
literally: Freezing the card [is] necessary

In smoother English, that becomes:

• It is necessary to freeze the card
• Freezing the card is necessary
• The card needs to be frozen
  (depending on context)

A very formal version would be:

من الضروري تجميد البطاقة

This means:

It is necessary to freeze the card

This structure is common in formal writing and official instructions:

• من الضروري = it is necessary
• تجميد البطاقة = freezing the card

So compared with the original:

• تجميد البطاقة ضروري = formal and concise
• من الضروري تجميد البطاقة = even more explicitly formal

Not necessarily. البطاقة just means the card.

Depending on context, it could be:

• a bank card
• a credit card
• a debit card
• an ID card
• another type of card

But because the sentence uses تجميد in an administrative sense, many learners would naturally think of:

• a bank card
• a payment card
• possibly a SIM or service card in some contexts

So the exact meaning depends on the surrounding situation.