In Spanish the dieresis sign makes that the letter "u" in güe, güi, has its own sound. Some words with dieresis are:

pingüino / penguin

paragüitas / little umbrella

yegüita / little mare
agüita
Cromagüita
In Mexico we use the diminutive for agua to express that the water will be specially delicious according the circumstances, for example if you've walked a lot under the hot sun then you might say:

Cuando llegue a casa me voy a tomar una rica agüita / When I get home I'll drink a delicious glass of water

Also it's used to mean an herbal tea or coffee.

Me voy a tomar una agüita caliente / I'll drink a delicious cup of tea / coffee
Diéresis.

lingüístico, ca.

vergüenza

bilingüe
I wanted to write the Spanish word diéresis in English and my dictionary says:

diéresis

f diaeresis; US dieresis.Emotion: smile
Sanz
I wanted to write the Spanish word diéresis in English and my dictionary says:

diéresis

f diaeresis; US dieresis.Emotion: smile

You are right. I didn't know you wanted to write it in English.
Also "agüita" is used in Mexico to express some nuisance when it's raining:

¡Ay, está dura el agüita! / Ouch, it's raining hard!