1. Small, delicate, or barely noticeable alterations or modifications
The artist made subtle changes to the painting that only experts could detect.
O artista fez mudanças sutis na pintura que apenas especialistas poderiam detectar.
2. Slight variations that are difficult to perceive but have significance
There were subtle changes in her tone of voice that suggested displeasure.
Havia mudanças sutis em seu tom de voz que sugeriam descontentamento.