Spanish Phrase
Sí, asegúrate de que tu caja sea resistente y nueva.
Meaning
The speaker is confirming something and then advising the listener to verify that their box is both sturdy and brand‑new. The use of the subjunctive (sea) adds a nuance of recommendation rather than stating a known fact.
When to use
Use this phrase when you want to give a friendly but firm reminder about the condition of an item—e.g., before shipping, moving, or storing something valuable. It works well in both casual conversation and more formal instructions.
✦Grammar Breakdown
Sí,asegúratedequetucajasearesistenteynueva.
Asegúrate (imperative reflexive)
‘Asegúrate’ is the affirmative tú‑imperative of the reflexive verb ‘asegurarse’. The reflexive pronoun ‘te’ is attached to the end of the verb.
de que + subjunctive
After ‘asegúrate de que’, the verb in the subordinate clause must be in the present subjunctive (sea) because the statement expresses a desired condition, not a fact.
Adjective agreement
‘Resistente’ and ‘nueva’ agree in gender and number with ‘caja’ (feminine singular).
Use of ‘Sí’ as confirmation
‘Sí’ at the beginning signals agreement or affirmation before giving a recommendation.
🗨In Conversation
¿Puedo usar esta caja para enviar los libros?
Can I use this box to ship the books?
Sí, asegúrate de que tu caja sea resistente y nueva.
Yes, make sure that your box is sturdy and new.
✕Common Mistakes
Sí, asegúrate de que tu caja es resistente y nueva.
After ‘de que’, the verb must be in the subjunctive, not the indicative.
Sí, asegura de que tu caja sea resistente y nueva.
The affirmative tú‑imperative of ‘asegurarse’ requires the reflexive pronoun attached: ‘asegúrate’.
Sí, asegúrate de que tu caja sea resistente y nuevo.
‘Caja’ is feminine, so the adjective must be ‘nueva’, not ‘nuevo’.
↔Alternatives
Sí, verifica que tu caja sea fuerte y nueva.
Yes, check that your box is strong and new.
Claro, confirma que la caja esté en buen estado y sea nueva.
Sure, confirm that the box is in good condition and is new.
Por supuesto, comprueba que la caja sea resistente y recién comprada.
Of course, check that the box is sturdy and freshly bought.
Cultural Tip
In Spanish‑speaking cultures, giving advice often starts with a confirming ‘Sí’ or ‘Claro’ followed by an imperative. The reflexive imperative (asegúrate) sounds more personal and polite than a direct command. Also, using the subjunctive after ‘de que’ is a hallmark of native‑like fluency; learners who replace it with the indicative ‘es’ sound less natural.