Teimosia vs. obstinação
While both words translate to stubbornness, teimosia is generally associated with a refusal to yield or change one's mind, often irrational or childish. In contrast, obstinação suggests a deep, relentless persistence toward a goal or belief, which can be viewed as either a flaw or a virtue like tenacity.
Teimosia
B1Teimosia is the most common word for stubbornness in daily conversation. It usually implies a negative or annoying resistance to advice, logic, or authority. It describes someone who refuses to change their stance simply because they do not want to give in, often regarding trivial matters.
Ele não quis pedir ajuda por pura teimosia.
(He did not want to ask for help out of sheer stubbornness.)
A teimosia da criança em não comer vegetais frustrou a mãe.
(The child's stubbornness in not eating vegetables frustrated the mother.)
Eu avisei que ia chover, mas a sua teimosia te deixou molhado.
(I warned you it was going to rain, but your stubbornness got you wet.)
Pare com essa teimosia e aceite que você errou o caminho.
(Stop this stubbornness and accept that you missed the turn.)
Obstinação
C1Obstinação implies a fierce, unshakeable adherence to a purpose, idea, or plan. It is a more formal and intense term. Unlike teimosia, which is often about stopping progress, obstinação is often about driving forward despite difficulties. It can be positive (tenacity/determination) or negative (blind persistence).
A obstinação do cientista levou à descoberta da cura.
(The scientist's tenacity led to the discovery of the cure.)
Ela estudou com obstinação para passar no exame difícil.
(She studied with determination to pass the difficult exam.)
Foi a sua obstinação cega que causou a falência da empresa.
(It was his blind obstinacy that caused the company's bankruptcy.)
Os atletas mostraram grande obstinação durante a maratona.
(The athletes showed great persistence during the marathon.)
Summary
Use teimosia for everyday situations where someone is being difficult, resisting change, or acting unreasonably mostly for the sake of pride. Use obstinação when describing a powerful will to pursue a specific objective, which implies a strong character trait rather than just a fleeting refusal to listen.