Disminuir vs. reducir vs. bajar

The Spanish words 'disminuir', 'reducir' and 'bajar' are often used interchangeably as they all carry the meaning of 'to decrease' or 'to lower'. However, they're typically used in different contexts and their usage may vary slightly depending on the situation.

Disminuir

'Disminuir' generally refers to decreasing in size, quantity, intensity, or importance.
La población disminuyó significativamente después de la guerra.
(The population significantly decreased after the war.)
El doctor me dijo que debería disminuir mi consumo de azúcar.
(The doctor told me I should decrease my sugar intake.)
La luz del sol comenzó a disminuir al atardecer.
(The sunlight began to decrease at sunset.)

Reducir

'Reducir' is often used when referring to lessening something in size, amount, number, or degree. Importantly, it can also imply transformation, not just decrease.
Estoy tratando de reducir mi huella de carbono.
(I'm trying to reduce my carbon footprint.)
El gobierno planea reducir los impuestos para los pequeños negocios.
(The government plans to reduce taxes for small businesses.)
El chef redujo la salsa a la mitad para concentrar el sabor.
(The chef reduced the sauce by half to concentrate the flavor.)

Bajar

'Bajar' carries a more physical connotation of moving something downwards or reducing in rank or level. It can be used in both literal and metaphorical contexts.
Debes bajar la temperatura del refrigerador.
(You should lower the refrigerator's temperature.)
Decidió bajar su nivel de estrés haciendo yoga.
(She decided to lower her stress level by doing yoga.)
La empresa decidio bajar el precio de sus productos.
(The company decided to lower the price of their products.)

Summary

While 'disminuir', 'reducir', and 'bajar' all convey the idea of making something smaller or lessening it in some way, each word imparts its own unique hue to this central meaning according to different contexts. 'Disminuir' generally pertains to quantitative or qualitative decrease, 'reducir' encompasses diminution but may also indicate transformation, while 'bajar' connotes a more physical sensation of moving downwards or reducing in rank or level.