1 {scene: Giuseppe’s pizzeria}
1 Ishmael: Hi Giuseppe. How’s things?
1 Giuseppe: Bah! I have the troubles with my computer.
2 Giuseppe: I have this thing to do when it is difficult to fix. Sudo.
3 Ishmael: Sudo? That’s incredibly dangerous if you don’t know what you’re doing!
4 Giuseppe: Sorry, I speak Italian. Sudo means “I sweat”.

In my ongoing quest to teach myself Italian, I keep running across new words to increase my vocabulary. Recently I learnt the verb sudare, which means "to sweat". Conjugating it to form the first person present tense gives sudo ("I sweat"). I was amused by the coincidence with the Unix command of the same spelling, and thought that was enough to try to make a joke. (Whether I succeeded or not is for others to judge...)

Looking up the word sudare, I was surprised to find that it is also a Japanese word, referring to blinds or screens, generally used to shield from direct sunlight.

Then I checked the entry for sudare in Wiktionary, and I saw this:

(intransitive, but takes avere as auxiliary) to sweat, perspire

Wait.... "intransitive, but takes avere as auxiliary"???

This goes against all the rules of Italian verb conjugation that I've painstakingly learnt over the past few years. I maintain a notebook of Italian grammar that I refer to when necessary when doing lessons. I have a page devoted to listing all of the rules, tricky cases, and outright exceptions to which auxiliary verb each verb takes.

For those who know little about Italian, or grammar in general, an auxiliary verb is a verb used to modify another verb. The one particular use that I'm concerned with here is to convert a verb to a past tense (or perfect tense, in grammatical jargon), although there are other auxiliary verbs that perform other jobs as well. In English, the verb used to make a past tense is "have". For example: "I eat" can become "I have eaten". (You can also say "I ate" in English, which is a different form of past tense, but not important right now.) So, in English, pretty much every verb takes "have" as the auxiliary for forming past tense. "I arrive" becomes "I have arrived".

In Italian, however, there are two different auxiliary verbs used for this purpose of forming a past tense: avere ("to have") and essere ("to be"). Which one to use is governed by a few grammatical rules. The main rule is that transitive verbs (verbs that involve you doing something to something else) take avere, while intransitive verbs (verbs that don't involve you doing something to something else) take essere. For example, mangiare ("to eat") is a transitive verb, because you can eat something.

• "I eat a sandwich" becomes Io mangio un panino.
• "I eat" becomes Io mangio.
• "I have eaten a sandwich" becomes Io ho mangiato un panino.
• "I have eaten" becomes Io ho mangiato (even though no specific eaten object is stated, the verb is still treated as transitive).

Where ho is the "I have" conjugation of avere ("to have").

And arrivare ("to arrive") is an intransitive verb, because you never "arrive something", you just "arrive".

• "I arrive" becomes Io arrivo.
• "I have arrived" becomes Io sono arrivato.

Where sono is the "I am" conjugation of essere ("to be"). In effect, in Italian, while the literal word-for-word translation of Io ho mangiato is "I have eaten", the literal word-for-word translation of Io sono arrivato is "I am arrived", rather than "I have arrived".

Okay, so, my notes include these rules, plus a couple of other corner case rules that aren't important right now, plus a couple of exceptions, specifically verbs that are transitive but take essere instead of avere.^[1]

I did not have any exceptions listed that are intransitive but take avere. Hopefully now you can see why I was so shocked at seeing that entry in Wiktionary. It's not just an exception to my hard learnt Italian grammar rules - it's an exception unlike any of the other exceptions that I've already learnt. If I hadn't seen that exception note, I would blithely have assumed sudare took essere as the auxiliary, and made sentences such as Io sono sudato (lit. "I am sweated") and assumed that it was correct. But no, it's actually Io ho sudato (lit. "I have sweated").

My hope in writing this long annotation about one peculiarity of Italian grammar is that I will now never forget that sudare is a bizarre exception to the auxiliary verb rules! There are probably a few more such exceptions outside my current Italian vocabulary, but at least when I run across them in future I can merely add them as additional examples under the trailblazing sudare.

[1] If you're curious what the exceptions are: diventare ("to become"), and piacere (kind of "to like", only backwards, it more literally means "to please" - in Italian you can't say "I like pizza", you have to say "Pizza pleases me". This is one of the weirdest and most difficult verbs for English speakers to master). There are probably a few more such exceptions outside my current Italian vocabulary.