האתר מחייב לבחור סיסמה חדשה כל שלושה חודשים.

מחייב comes from the root ח־י־ב and here means requires, obligates, or makes it necessary.

In this sentence, האתר מחייב... means the site is imposing a requirement. It is stronger than just suggests or recommends.

So:

• האתר מחייב = the site requires
• not just the site asks

לבחור is the infinitive, meaning to choose.

After a verb like מחייב (requires), Hebrew often uses an infinitive:

• האתר מחייב לבחור... = The site requires [someone] to choose...

This is very similar to English:

• requires choosing
• requires you to choose

So the structure is:

• מחייב + infinitive
• requires + to choose

Hebrew often leaves this kind of subject unstated when it is obvious from context.

So האתר מחייב לבחור סיסמה חדשה literally feels like:

• The site requires choosing a new password

But in natural English, we usually say:

• The site requires you to choose a new password

The you is understood from the situation, even though it is not written in Hebrew.

את marks a definite direct object in Hebrew.

Here, סיסמה חדשה means a new password, which is indefinite, so there is no את.

Compare:

• לבחור סיסמה חדשה = to choose a new password
• לבחור את הסיסמה החדשה = to choose the new password

So the absence of את tells you the password is not a specific already-known one.

Because סיסמה is a feminine singular noun, the adjective must agree with it.

So:

• סיסמה = feminine singular
• חדשה = feminine singular adjective, meaning new

Hebrew adjectives usually come after the noun and agree in:

• gender
• number
• definiteness

So:

• סיסמה חדשה = a new password
• הסיסמה החדשה = the new password

In Hebrew, adjectives normally come after the noun they describe.

So:

• סיסמה חדשה = literally password new
• natural English: new password

This is the normal Hebrew word order for noun + adjective.

Examples:

• בית גדול = big house
• מכונית אדומה = red car
• סיסמה חדשה = new password

כל means every in this sentence.

So:

• כל שלושה חודשים = every three months

This phrase expresses repeated time intervals.

Examples:

• כל יום = every day
• כל שבועיים = every two weeks
• כל שלושה חודשים = every three months

Because חודשים is a masculine noun, and Hebrew numbers 3–10 use the form that matches the noun in the standard way taught for counting:

• masculine noun → שלושה
• feminine noun → שלוש

So:

• שלושה חודשים = three months
• but שלוש דקות = three minutes

Since חודש is masculine, the sentence correctly uses שלושה.

Yes.

• חודש = month
• חודשים = months

This is a masculine plural ending in -ים.

So:

• שלושה חודשים = three months

Yes. האתר means the site or the website.

It is made of:

• אתר = site
• ה־ = the

So:

• אתר = a site
• האתר = the site

In context, this usually means the website or the system you are using.

The structure is:

• האתר = subject = the site
• מחייב = verb = requires
• לבחור = infinitive = to choose
• סיסמה חדשה = object of the infinitive = a new password
• כל שלושה חודשים = time expression = every three months

So the whole sentence is built like this:

The site requires [someone] to choose a new password every three months.

That structure is very natural in Hebrew.

Yes, that is possible in some contexts, but requires is usually the best translation.

מחייב can sometimes feel like:

• requires
• obligates
• forces

For a website policy, requires sounds the most natural in English.

So:

• best everyday translation: The site requires you to choose a new password every three months.
• more literal/stronger option: The site obligates you to choose a new password every three months.

Then both the noun and adjective would become definite:

• הסיסמה החדשה = the new password

So the sentence would be:

• האתר מחייב לבחור את הסיסמה החדשה...

But that would usually imply a specific known password, which does not really fit the usual meaning here.

The original sentence uses סיסמה חדשה because it means a new password, not a specific one.