What's the "ísimo" doing on the following adjectives?
What rules should be applied to convert the adjectives to the corresponding "ísimo" adjective?
Example 1:
El pastel está rico.
El pastel está riquísimo.
Example 2:
El café está caliente.
El café está calentísimo.
More examples: buenísimo, facilísimo, malísimo.
ísimo/ma is a Latin suffix that can be appended to some adjectives and adverbs to form their superlatives: malísimo, riquísimo.
The rules governing the use of the ísimo suffix are the following:
For adjectives ending in l, r, and z, simply add the suffix (changing the final z for a c):
fácil, facilísimo.
feroz, ferocísimo.
popular, popularísimo.
As an exception to this rule, if the adjective ends in or, the c consonant must be added before the suffix: mayor, mayorcísimo.
Adjectives ending in n usually add a consonant c before the suffix:
bribón, briboncísimo.
cansón, cansoncísimo.
Adjectives ending in a non-tonic vowel usually lose the vowel:
listo, listísimo.
dulce, dulcísimo.
As an exception the superlative of cursi is cursilísimo.
If the adjective ends in a tonic vowel, the superlative cannot be formed using the -ísimo suffix
carmesí, muy carmesí.
Adjectives ending in the non-tonic groups ue, or uo/ua lose the final vowel:
tenue, tenuísimo.
ingenuo, ingenuísimo
exigua, exigüísima.
Adjectives ending in diphthongs io/ia lose both vowels:
amplia, amplísima.
sucio, sucísimo.
Adjectives ending in hiatus ío/ía lose the final vowel:
frío, friísimo.
impía, impiísima.
A special case is the group of adjectives containing the diphthong ie o ue; those adjectives form their superlatives (with ísimo) using the Latin root of the corresponding adjective:
cierto, certísimo.
fuerte, fortísimo.
caliente, calentísimo.
However, this group also admits another valid form for the superlative, incorporating the Spanish root of the adjective:
cierto, ciertísimo
fuerte, fuertísimo.
caliente, calientísimo.
Some other superlatives come directly from Latin:
antiquísimo (lat. antiquissimus).
crudelísimo (lat. crudelissimus).
The rules can be found in the entry for ísmo in the Diccionario panhispánico de dudas.
It's is worth noticing that there's another way (less prone to error) to produce the superlative without appending the ísmo suffix, namely, using muy:
caliente, muy caliente.
fuerte, muy fuerte.
falaz, muy falaz.
Actually Gonzalo's nice answer doesn't cover one part of the story fully.
It's not that Spanish has two ways to express the superlative of adjectives - rather Spanish, like Latin, most modern Romance languages, and also Ancient Greek has two different kinds of superlatives:
(There is a small possibility that the terms used in English for this part of Spanish grammar follow a different tradition to what is used in Spanish when discussing Spanish grammar...)
I am going to expound on the 'Mejcanisimo' nature of the subject in my answer. I can tell that too many answers become contradictory in the end as the answers are taken from books written by Authors of differing opinions. This may be OK for someone who does not live the life of a Mexican every day on the border, which is to say that you cannot get any more Mexican than the border. Books are fine, however they completely fail to capture the true essence of the subject. The proper use in Mexican is that 'isimo' refers to the essence of something and expresses the degree of how you feel. 'Muchisimo Gracias' is a way of politely expressing thankfulness of a greater degree. It expresses a feeling and not particularly thought.
Hermano Gonzalo, you rely too much on grammatical rules taken from books and not from real life. Your word 'ciertisimo' may follow your books rule however, it is not a real word. The word Truth is truth in Spanish whether in Spain or Mexico and truth has no varying degree as lack of truth is a lie. That makes it a closed end statement or question, one where the question or statement is yes or no so truth cannot have differing degrees, sorry if I offend you. So when daily life does not hold true to books, is it not real? Books are written to educate and use as a guide, but the rules cannot be used in all real instances depending on the word and in the context of which it is used. Anything that is absolute in nature of context, cannot vary in any degree, therefore the correct rule of thumb would be to ascertain whether the word has a value of being absolute, if so, then it cannot be exponentially uncreased in any way, regardless of what any book says. Keep in mind that many books are written by linguistic majors who have learned from someone else's book and then write their own take on other's books. I do NOT own a single book on Spanish and only teach from verifiable usages through real life experience. So if I seem abrasive, forgive me I AM MEXICAN and can only give real life experience of over half a century of living on the border of Mexico and living the Mexican lifestyle in real-time. Hasta luego compadres.
