Although aun and aún are adverbs that look much alike and can each be translated sometimes by the English adverb "even," they have different meanings and should not be confused with each other. (Interestingly, though, even native speakers often confuse the two.)
Aun, which is usually synonymous with incluso, is frequently translated as "even" when it indicates that what follows is included in a category. Examples should make this concept clearer; the parenthetical translations below aren't the way you necesarily should translate these sentences but are included to indicate the meaning of aun:
- Seré la única que estaré allí aun si hace frío. I will be the only one who is there even if it is cold. (I will be the only one there including if it's cold.)
- Aun así, no puedo hacerlo. Even so, I can't do it. (Including those circumstances, I can't do it.)
- Aun hoy te recuerdo. Even today I remember you. (Including today I remember you.)
- Sus fotos son muy inferiores aun con una cámara cara. His photos are very inferior, even with an expensive camera. (His photos are very inferior, including with an expensive camera.)
Aún, on the other hand, is used to indicate that an action or status is continuing. With this usage, it is often synonymous with todavía and can be translated as "still" or "yet."
- El mundo aún está en peligro. The world is still in danger.
- ¡Aún no lo creo! I still don't believe it!
- No he visto aún la película, pero el libro me encantó. I haven't seen the movie yet, but I loved the book.
- El peso aún puede apreciarse. The peso can still gain value.
In comparisons, usually ones using más or menos, aún can be translated as "still" or "even." Note that aun isn't used this way in comparisons.
- Quiero hacer aún más verde el césped. I want to make the lawn even greener.
- El sector industrial genera aún menos empleo que la agricultura. The industrial sector generates even fewer jobs than agriculture does.
- La mujer que brillaba aún más que el sol (título de libro). The Woman Who Outshone the Sun (book title).