صديقتي تريد أن تذهب إلى الجامعة اليوم، لكنها مريضة.

صديقة means female friend. The ending ـي means my, so صديقتي means my female friend.

A useful pronunciation point: the ة in صديقة is normally a tāʾ marbūṭa, but when a suffix is added, it is pronounced as a real t sound. So this is pronounced roughly ṣadīqatī, not ṣadīqaī.

In the present tense in Arabic, the prefix تـ can mark more than one form. It is used for:

• she
• you masculine singular
• you feminine singular, with a different ending

So in this sentence, تريد means she wants because the subject is صديقتي.

Compare:

• يريد = he wants
• تريد = she wants or you want masculine singular, depending on context

Here the context makes it clearly she wants.

Arabic often does not use a separate subject pronoun when the verb already shows the subject.

So تريد already contains the meaning she wants. Since صديقتي is stated explicitly, there is no need to add هي.

In other words, Arabic commonly says the equivalent of:

• My friend wants...

rather than

• My friend, she wants...

Although Arabic can use هي for emphasis, it is not needed here.

أن introduces another verb after verbs like want, like, need, and similar expressions.

Here it works a lot like English to in wants to go.

So:

• تريد = she wants
• أن تذهب = to go

A more literal explanation would be something like she wants that she go, but in natural English we simply say she wants to go.

Yes. After أن, the following present-tense verb is normally in the subjunctive.

In fully vowelled Arabic, this would be written as تذهبَ with a final fatḥa. In normal everyday writing without short vowels, it still appears as تذهب, so you do not see the change in spelling.

That means:

• written without vowels: تذهب
• fully vowelled after أن: تذهبَ

This is a very common feature of Modern Standard Arabic.

The verb ذهب normally uses إلى to express destination in MSA.

So:

• ذهب إلى... = went to...
• تذهب إلى... = goes / is going to...

That is why إلى is used before الجامعة.

الجامعة means the university. In Arabic, it is very natural to use the definite article here, especially when the place is understood from context.

English often says go to university or go to college without the, but Arabic commonly uses الـ in this kind of sentence.

So:

• إلى الجامعة = to the university
• إلى جامعة = to a university

The second version is possible in some contexts, but it sounds more indefinite, as if you mean some university, not the usual one.

اليوم means today. It is an adverb of time.

In this sentence, it comes after إلى الجامعة, which is completely natural:

• صديقتي تريد أن تذهب إلى الجامعة اليوم

Arabic does allow some flexibility, so you may also see اليوم in other positions for emphasis or style. But the position here is simple and very common.

لكنها is made of two parts:

• لكنّ = but / however
• ها = she / her as an attached pronoun

So لكنها means but she...

In fully vowelled writing, it is often shown as لكنّها. In normal unvowelled writing, you usually just see لكنها.

Because the person being described is feminine.

Arabic adjectives agree with the noun in gender and number. Since صديقتي is feminine singular, the adjective must also be feminine singular:

• مريض = sick masculine
• مريضة = sick feminine

So لكنها مريضة means but she is sick.

In the present tense, Arabic usually does not use a separate word for is / am / are.

So:

• هي مريضة literally looks like she sick
• but it means she is sick

That is standard Arabic grammar. If you want the past or future, then Arabic uses other forms, but in the present tense the linking verb is normally omitted.

Yes. Arabic allows more than one word order.

The given sentence begins with the noun:

• صديقتي تريد أن تذهب...

But you could also say:

• تريد صديقتي أن تذهب...

Both are possible in MSA. Starting with صديقتي makes the sentence feel more topic-first, as if you are introducing my friend and then saying something about her. The version in your sentence is very natural and easy for learners to follow.