Questions & Answers about Este é o único problema.
Este is a demonstrative, meaning this.
A quick comparison:
- este = this
- esse = that
- isto = this/that without a noun after it
In Este é o único problema, este stands alone like this one or this in English.
A few useful notes for Brazilian Portuguese:
- In formal grammar, este is used for something closer to the speaker, and esse for something closer to the listener or something already mentioned.
- In everyday Brazilian speech, many people use esse where a textbook might prefer este.
So Este é o único problema is perfectly correct, but in casual speech you may also hear Esse é o único problema.
Because Portuguese usually uses ser for identity, definition, and classification, and estar for temporary states or conditions.
Here, the sentence is identifying something:
- Este é o único problema = it is being identified as the only problem
So é (from ser) is the natural choice.
Compare:
- Ele é médico. = He is a doctor.
- Ele está cansado. = He is tired.
In your sentence, the speaker is not describing a temporary condition. They are saying what this is.