يعيد صديقي تعيين كلمة المرور.

Because a very common Arabic word order is verb + subject + object.

So:

يعيد صديقي تعيين كلمة المرور
literally follows: resets my-friend the password

This is normal in Modern Standard Arabic. You could also say:

صديقي يعيد تعيين كلمة المرور

That version is also correct, but it puts a bit more emphasis on my friend.

يعيد is the imperfect (non-past) form of the verb أعاد.

• أعاد = he repeated / restored / did again
• يعيد = he repeats / he is repeating / he will repeat-do

In this sentence, it helps form the idea of resetting.

Grammatically, يعيد is:

• 3rd person
• masculine
• singular

That matches صديقي = my friend (masculine singular).

Because Arabic often expresses this idea as redo the setting/assignment rather than with a single simple verb.

• يعيد = repeats / does again
• تعيين = setting, assigning, specifying

So يعيد تعيين literally means something like:

re-does the setting of

In technical Arabic, this is a very common way to say reset.

So:

يعيد تعيين كلمة المرور
= resets the password

A learner should treat يعيد تعيين as a common technical expression.

تعيين is a verbal noun (called a maṣdar) from عيّن.

Depending on context, تعيين can mean things like:

• assigning
• determining
• specifying
• setting

In technology language, it often means setting or assigning a value.

So in this sentence:

يعيد تعيين كلمة المرور
means resets the password

Even though تعيين can have other meanings in other contexts, here it is clearly the technical sense.

It is made from:

• صديق = friend
• ـي = my

So:

صديق + ي = صديقي
= my friend

Arabic very often uses attached pronoun suffixes like this instead of a separate word for my.

Some similar examples:

• كتابي = my book
• اسمي = my name
• هاتفي = my phone

Because in Arabic, possession is often shown with a suffix attached directly to the noun.

So instead of saying something like my + friend as two separate words, Arabic usually says:

صديقي = friend-my

This is one of the most important patterns in Arabic.

Common possessive suffixes include:

• ـي = my
• ـك = your
• ـه = his
• ـها = her

So:

• صديقي = my friend
• صديقك = your friend
• صديقه = his friend

Yes. صديق is the masculine form meaning male friend.

If you wanted my female friend, you would say:

صديقتي

And then the verb would normally be feminine too:

تعيد صديقتي تعيين كلمة المرور
= My female friend resets the password

So the original sentence suggests a male friend.

This is an iḍāfa construction, often called a construct phrase.

It is made of:

• كلمة = word
• المرور = the passing / passage

Together:

كلمة المرور
literally: word of passage
naturally: password

This is a very common Arabic way of building noun phrases.

A key rule of iḍāfa is:

• the first noun usually does not take ال
• the second noun can take ال
• the whole phrase can still be definite

So كلمة المرور is definite even though كلمة itself does not have ال.

Because in an iḍāfa construction, the first noun normally does not take ال.

So:

• correct: كلمة المرور
• not normally: الكلمة المرور

That is just how the structure works.

The definiteness of the whole phrase comes from the second noun:

• كلمة مرور = a password
• كلمة المرور = the password

So even without ال on كلمة, the whole phrase can still mean the password.

The Arabic imperfect can cover several meanings, depending on context.

So يعيد could mean:

• resets
• is resetting
• will reset

Without extra context, English could translate it in more than one way.

In a plain sentence like this, resets or is resetting are both reasonable depending on the intended meaning.

If Arabic wants to make future meaning clearer, it can use words like:

• سـ
• سوف

For example:

سيعيد صديقي تعيين كلمة المرور
= My friend will reset the password

A careful full reading would be approximately:

yuʿīdu ṣadīqī taʿyīna kalimata l-murūr

A few useful notes:

• يعيد = yuʿīdu
• صديقي = ṣadīqī
• تعيين = taʿyīna here, because it is the object of يعيد
• كلمة in كلمة المرور is pronounced kalimata in connected speech because it is in an iḍāfa
• المرور = al-murūr, and because م is a moon letter, the l sound of al- stays pronounced

In normal writing, these short vowels are usually not written.

Not naturally.

يعيد صديقي كلمة المرور would more likely sound like:

• My friend repeats the password, or
• My friend restores/brings back the password

It does not sound like the normal technical expression for reset the password.

For reset the password, the common expression is:

• يعيد تعيين كلمة المرور
• or in some contexts يعيد ضبط كلمة المرور

So for a tech meaning, keep تعيين.

Yes, that is a good idea.

In technical Arabic, learners will very often see expressions like:

• إعادة تعيين كلمة المرور = password reset / resetting the password
• أعد تعيين كلمة المرور = reset the password
• يعيد تعيين كلمة المرور = he resets / is resetting the password

This is one of those combinations that is more useful to learn as a chunk than word-by-word every time.