Using a diacritic often signals that a word is a "loanword" from another language (e.g., frappé or açai ).

Changes a hard "k" sound to a soft "s," found in façade or garçon .

Used in English primarily for poetic effect to show an extra syllable is pronounced, like learnèd .

why learned is not learnèd, and why no one uses noöne. : r/linguistics