Flecha vs. seta
While both seta and flecha translate to "arrow" in English, they are used in distinct contexts. Generally, flecha refers to the physical weapon composed of a shaft and a sharp point, typically used with a bow. In contrast, seta most commonly refers to the graphical symbol, a directional sign, or the turn signal on a vehicle.
Flecha
B1This word primarily refers to the projectile weapon shot from a bow (arco). It implies the physical object made of wood, carbon, or metal with feathers at the end. It is also used metaphorically to describe something moving at great speed.
O arqueiro disparou a flecha e acertou o centro do alvo.
(The archer shot the arrow and hit the center of the target.)
Nas histórias antigas, os guerreiros lutavam com arco e flecha.
(In ancient stories, warriors fought with bow and arrow.)
O carro passou por nós rápido como uma flecha.
(The car passed by us fast like an arrow.)
Dizem que o Cupido une casais com uma flecha mágica.
(They say Cupid unites couples with a magical arrow.)
Seta
A2This word usually refers to a graphical symbol used to indicate direction, such as on a road sign or a computer screen. Crucially, in Brazil, seta is the specific term for a car's turn signal (blinker). Historically, it can refer to a dart or a short projectile, but common usage leans heavily toward symbols.
Você deve ligar a seta antes de fazer uma curva com o carro.
(You must turn on the blinker before making a turn with the car.)
Siga a seta vermelha para encontrar a saída de emergência.
(Follow the red arrow to find the emergency exit.)
A seta do mouse não está se movendo na tela do computador.
(The mouse cursor is not moving on the computer screen.)
O gráfico mostra uma seta apontando para cima.
(The chart shows an arrow pointing upwards.)
Summary
Use flecha when talking about the weapon, archery sports, or metaphorical speed. Use seta when talking about symbols, traffic signs, computer cursors, or the turn signal lights on a vehicle.