Incendio vs. fuego
The words 'incendio' and 'fuego' are often used interchangeably in Spanish to refer to a fire, but there are nuances between their uses.
Incendio
'Incendio' is used primarily to describe uncontrolled, large scale and often disastrous fires. This term is typically used when referring to wildfires or building fires.
El incendio en el bosque está fuera de control.
(The forest fire is out of control.)
El incendio del edificio causó grandes pérdidas.
(The building fire caused great losses.)
Fuego
'Fuego' is a more general term for 'fire'. It can be used metaphorically or literally and does not necessarily imply destruction. However, it can also refer to dangerous, uncontrolled fires in some contexts.
¡Por favor, apaga el fuego!
(Please, put out the fire!)
Jugar con fuego es peligroso.
(Playing with fire is dangerous.)
El fuego en la chimenea me tranquiliza.
(The fire in the fireplace relaxes me.)
Summary
'Incendio' and 'fuego' both refer to a situation where something is burning. However, 'incendio' is more specific to uncontrolled, often large-scale and disastrous fires such as wildfires or building fires. On the other hand, 'fuego' is used as a general term for any type of fire and it can also be used metaphorically.