Dacă îți este sete, cere apă rece.

Dacă means if. It introduces a condition:

Dacă îți este sete = If you are thirsty

So the whole sentence is built like:

If X, do Y.

Romanian often expresses physical states with a structure that is closer to to someone is thirst/hunger than to English to be thirsty/hungry.

So:

• îți este sete = literally something like to you is thirst
• natural English: you are thirsty

This is a very common Romanian pattern:

• îmi este foame = I am hungry
• îmi este somn = I am sleepy
• îmi este frig = I am cold

So sete is a noun meaning thirst, not an adjective.

îți is the unstressed dative pronoun meaning to you.

In îți este sete, it marks the person experiencing the state:

• îmi este sete = I am thirsty
• îți este sete = you are thirsty
• îi este sete = he/she is thirsty

So even though English uses you are, Romanian uses a structure that includes to you.

Yes. Este and e both mean is.

• îți este sete = a bit fuller / slightly more careful
• ți-e sete or îți e sete = very common in everyday speech

All of these are natural:

• Îți este sete
• Îți e sete
• Ți-e sete

The sentence in your example uses the fuller form este.

Romanian often drops subject pronouns when they are not needed, because the verb form and the context already make the subject clear.

Here, îți already shows that the sentence is about you, and the imperative cere also implies you.

So:

• Dacă îți este sete, cere apă rece. = normal
• Dacă tu îți este sete... = wrong
• Dacă tu ești însetat... = possible in another structure, but tu would usually only be added for emphasis

Romanian uses subject pronouns less often than English.

Cere is the 2nd person singular imperative of a cere = to ask for / request.

So it means:

• cere! = ask for! / request!

This is the command form used when speaking to one person informally.

Related forms:

• a cere = to ask for
• cer = I ask for
• ceri = you ask for
• cere = he/she asks for
• cere! = ask for! (to one person)

Because a cere normally takes a direct object in Romanian.

English says:

• ask for water

Romanian says:

• cere apă = literally ask water, but naturally ask for water

So you should not add a separate word for for here.

Other examples:

• Cer ajutor. = I ask for help.
• Cere pâine. = Ask for bread.

In Romanian, adjectives usually come after the noun.

So:

• apă rece = cold water
• casă mare = big house
• om bun = good person

Putting the adjective before the noun is sometimes possible, but it often sounds more literary, emotional, or marked. The normal everyday order here is apă rece.

Yes, Romanian adjectives agree with the noun in gender and number.

Here:

• apă is feminine singular
• rece is the matching adjective form

In this case, rece looks the same for masculine/feminine singular in many contexts, so there is no obvious extra ending to notice.

Examples:

• apă rece = cold water
• ceai rece = cold tea
• băuturi reci = cold drinks

So the adjective still agrees, even if the form is not very different.

Yes, absolutely. That is very natural and common in spoken Romanian.

This is just a contraction:

• îți este → ți-e

So these are all possible:

• Dacă îți este sete, cere apă rece.
• Dacă îți e sete, cere apă rece.
• Dacă ți-e sete, cere apă rece.

They all mean the same thing. The differences are mainly about style and spoken rhythm.

It is informal singular, because cere is the command form used when speaking to one person in an informal way.

If you were speaking politely or to more than one person, you would use:

• Dacă vă este sete, cereți apă rece.

So:

• cere = informal singular
• cereți = plural or polite singular/plural

Yes, but the most common pattern is with a fi:

• mi-e sete = I am thirsty
• ți-e sete = you are thirsty

There is also the adjective însetat / însetată = thirsty, but it is often less common in everyday basic speech than the mi-e sete pattern.

So a learner should definitely remember:

• Mi-e sete
• Ți-e sete
• Îi e sete

These are extremely useful everyday expressions.

A rough pronunciation guide is:

DUH-kuh its yeh-STEH SEH-teh, CHEH-reh AH-puh REH-cheh

A few important sound notes:

• ă in Dacă and apă is a short central vowel, like a relaxed uh
• î in îți is a deeper central vowel that does not really exist in English
• ț is pronounced ts
• ce in cere and rece sounds like che in check, but shorter

A more natural Romanian rhythm would sound something like:

Dacă îți este sete, cere apă rece.

with the pause after sete.