With an adjective, ser describes a lasting quality and estar describes how someone is right now. Ele é nervoso means he is a nervous person; ele está nervoso means he is feeling nervous today. Feelings almost always take estar.
Examples
- Hoje estou cansada.
- Today I am tired.
- Ela é uma pessoa calma.
- She is a calm person.
- Estão felizes com a casa nova.
- They are happy with the new house.
The mistake to avoid
É aborrecido means he is boring; está aborrecido means he is bored.
Where this fits in
Body, health & feelings, Portuguese A2: Talk about your body, common illnesses, and how you feel. Visit a doctor or pharmacy and describe symptoms.