subtle
adj.adj. not obvious, loud, or easy to notice. It describes something that is delicate, clever, or has small but important differences.
adj. Delicate, faint, or difficult to perceive or describe; not obvious or direct. It can also describe a clever or indirect quality.
There is a subtle difference between them.
The artist used subtle changes in color to create a feeling of calm in the painting.
Her performance was a masterpiece of subtle gestures, conveying a universe of emotion with just a slight tilt of her head or a brief flicker of her eyes.
The adjective is derived from Middle English sotil, soubtil, subtil (“of a person, the mind, etc.: clever, ingenious, penetrating; cunning, sly; insidious; delicate, fine; not dense, light, thin; finely powdered; narrow, slender; etc.”), borrowed from Anglo-Norman sotel, subtil, sutil, Middle French soutil, subtil, sutil, and Old French sotil, soutil, subtil, sutil (“of an object: skilfully designed or made; delicate, fine; slender, thin; of an intangible thing: difficult to understand; of a person: discerning, shrewd; devious, sly; etc.”) (modern French subtil), from Latin subtīlis (“of texture: delicate, fine; slender, thin; accurate, keen; having fine judgment; etc.”), from sub (“below, under”) + tēla (“warp (threads running lengthwise in a loom); web”) (ultimately from Proto-Indo-European tetḱ- (“to create, produce; to cut, hew”), from teḱ- (“to beget, sire”)). The word displaced Old English smēag (literally “creeping”). The modern and Middle English (and French) spellings with -b- are influenced by Latin subtīlis; the letter was probably never pronounced. The noun is derived from Middle English sotil, soubtil, subtil (“wise person; sophisticated people collectively”), from the adjective.
Partly from both of the following: * From Middle English sotilen, subtile, subtilien (“to reflect on (something); to become mentally keen; to connive, scheme; to contrive, invent; to become pure or thin; to (cause something to) become light or thin; (medicine) to lighten or reduce (a diet)”), from Anglo-Norman sotiller, soutiller, sutiller, Middle French soutiller, soutillier, and Old French soutillier (“to make thin; to sharpen; to split hairs when arguing; to scheme, plot”), from Old French sotil, soutil, subtil, sutil (noun) (see etymology 1) + -ier (suffix forming infinitives of first-conjugation verbs), partly influenced by Late Latin subtīliāre, the present active infinitive of subtīliō (“to act craftily; to diminish”), from Latin subtīlis (adjective) (see etymology 1) + -ō (suffix forming regular first-conjugation verbs). * From subtle (adjective).