adjective
subtle
SUT-uhl/ˈsʌtl/
Delicate or slight enough to be difficult to notice.
The pale blue rim creates a subtle difference between the cream cups.

Etymology
The “under” and “web” elements evoke fine weaving; Watkins interprets the image as a fine thread passing under the warp. Physical fineness extends to qualities so delicate that they require careful attention.
In context
most obvious doubling you'll ever see on a coin. If you look closely, the letters almost look like they're vibrating. Like a shadow sitting right next to them. It's not subtle. It's loud.
More examples
- There is a subtle difference between these two shades of blue.
- I notice a subtle change in his tone.
- The pattern is so subtle that it disappears in dim light.
Forms
subtle · subtler · subtlest
subtly adverb — In a way that is difficult to notice.
subtlety noun — The quality of being difficult to notice.