Diminuer vs. décroître

Both 'diminuer' and 'décroître' are French verbs that relate to the concept of reduction in size, quantity, or intensity. However, they are used in different contexts and have subtle nuances in meaning.

Diminuer

To decrease in a broad sense, applicable to size, quantity, amount, intensity, or even abstract concepts. It is a more general term and can be used in a wide variety of contexts.
La luminosité de l'écran doit diminuer pour économiser la batterie.
(The screen brightness needs to decrease to save battery.)
Les prix ont commencé à diminuer après les fêtes.
(Prices started to decrease after the holidays.)
Il a réussi à diminuer le volume de la musique sans offenser le DJ.
(He managed to lower the volume of the music without offending the DJ.)
Pour diminuer le stress, elle pratique la méditation quotidiennement.
(To reduce stress, she practices meditation daily.)

Décroître

To decrease with a connotation of a gradual or natural decline. Often used for things that diminish over time and is less commonly applied to abstract concepts compared to 'diminuer'.
La population du village a commencé à décroître avec l'exode des jeunes vers les villes.
(The village's population began to decline with the exodus of young people to the cities.)
Le jour commence à décroître dès le solstice d'été.
(Daylight begins to decrease after the summer solstice.)
Suite à la maladie des plantes, leur production a nettement décru ces derniers mois.
(Due to plant disease, their production has noticeably decreased over the past few months.)

Summary

In summary, while both 'diminuer' and 'décroître' convey the idea of decreasing or becoming smaller, 'diminuer' is more versatile and can apply to a broad range of contexts including abstract ideas, whereas 'décroître' implies a more gradual or natural decrease over time and is generally used for tangible items such as population or daylight duration. Understanding these distinctions helps in choosing the appropriate verb based on the context of what is decreasing and how it is decreasing.