اختي بتسقي الريحان.

A rough pronunciation is okhti bitisʔi r-reḥān.

A few notes:

• اختي = okhti or ukhti depending how narrowly you transliterate it.
• بتسقي is often pronounced something like bitisʔi. In fast speech, the middle vowel may get reduced.
• الريحان is written with الـ, but because ر is a sun letter, it is pronounced more like er-reḥān than el-riḥān.

So the whole sentence sounds roughly like:

okhti bitisʔi r-reḥān

Because -ي at the end means my.

So:

• أخت / اخت = sister
• أختي / اختي = my sister

This is very common in Arabic: possession is often shown with a suffix attached directly to the noun.

Examples:

• بيتي = my house
• كتابي = my book
• اختي = my sister

In careful spelling, especially in Modern Standard Arabic, you would normally see أختي with a hamza.

In everyday writing, especially in colloquial Egyptian Arabic, people often leave off the hamza in writing, so اختي is very common.

So:

• أختي = more careful/standard spelling
• اختي = very common informal spelling

They mean the same thing here.

Because Egyptian Arabic usually does not use a separate present-tense verb to be the way English does.

Instead, the verb itself carries the meaning.

So بتسقي can mean:

• she waters
• she is watering

The exact English translation depends on context.

That is very normal in Egyptian Arabic. You do not need a separate word for is in this kind of sentence.

The بـ is a very common Egyptian Arabic marker for the present / habitual / ongoing verb form.

So:

• تسقي = a present-form base
• بتسقي = the normal Egyptian present meaning she waters / she is watering

In simple learner terms, بـ helps make this the everyday present tense in Egyptian Arabic.

The تـ part of the verb is the key clue.

In the present tense, Egyptian Arabic uses prefixes to show the subject. Here, تـ can be used for:

• she
• you (singular)

So بتسقي by itself could mean either:

• she waters / is watering
• you water / are watering (to one female)

But once you say اختي before it, the meaning is clear:

• اختي بتسقي = my sister is watering / waters

So the noun اختي tells you the subject is she.

Because this verb comes from the verb سقى meaning to water / give to drink, and in the present tense this kind of verb often shows a final -ي sound.

So the -ي here is part of the verb, not a separate word and not the possessive my.

That is an important point, because learners often see ي and wonder if it means my. Here it does not. It is just part of the verb form بتسقي.

Because in many Egyptian Arabic varieties, especially Cairene Egyptian, ق is often pronounced as a glottal stop ʔ.

So although the word is written:

• بتسقي

it is often pronounced more like:

• bitisʔi

not like a formal Standard Arabic q sound.

This is very normal in Egyptian Arabic spelling and pronunciation: the word may keep the letter ق in writing, but the spoken pronunciation changes.

Because ر is a sun letter.

When الـ comes before a sun letter, the ل sound assimilates into the next consonant.

So:

• written: الريحان
• pronounced: er-reḥān

The spelling stays the same, but the pronunciation changes.

This same thing happens in many other words, for example:

• الشمس → pronounced esh-shams
• الراجل → pronounced er-rāgil

Yes. اختي بتسقي الريحان is a very natural Egyptian Arabic word order.

It is:

• subject: اختي
• verb: بتسقي
• object: الريحان

Egyptian Arabic very often uses subject–verb–object in everyday speech, especially in conversational sentences like this one.

So starting with اختي is completely normal.

Because a noun with a possessive suffix is already definite.

So اختي already means my sister, which is automatically definite. You do not need an extra word for the.

Compare:

• أخت = a sister / sister
• أختي = my sister

Once the noun is possessed, it is already specific.

Because this is Egyptian Arabic, not formal Modern Standard Arabic.

In everyday Egyptian speech, the case endings used in Standard Arabic are normally not pronounced. So you simply say:

• اختي بتسقي الريحان

without final endings like -u, -a, or -i on each word.

That is one big difference between spoken Egyptian Arabic and formal written Arabic.