User:LjL/Italian vs Spanish

Difficulties of Italian

 * Verbs "essere" and "avere" are used as auxiliaries of other verbs for composite tenses in a way that's not intuitive at all, and for a few verbs you just have to know it, there is no clear "reason". Spanish always uses "haber".
 * Plurals are a little harder: -a becomes -e, -o becomes -i, -e becomes -i, words ending in accented vowels or consonants don't change... with exceptions. Spanish is always just -s (if ending in vowel) or -es (if ending in consonant). Additionally, plurals in -ci vs -chi and -gi vs -ghi can often seem arbitrary: "amico" (friend) becomes "amici", but "carico" (charge, load) becomes "carichi".
 * There are more definite articles, dependings on what sounds the following words starts with, in non-trivial ways: il, lo, l', la, i, gli, le. Spanish just has el, los, la, las.
 * There are some verbal clitics that are non-obvious: ne (roughly "of it", or "about it"), ci/vi (can be "us", but also "here", "there", but sometimes also "about it" like "ne", confusingly: for example, "cosa ne pensi?" = "what do you think about it?", but "ci penso" = "I'll think about it"), and they combine in more complex ways (gli/le + ne = "gliene"). Catalan is similar but even worse. Spanish just has lo(s), la(s), le(s), which of course also exist in Italian anyway.
 * Orthography is less transparent: you can't know where the stress of a word lies if you read it written (except in a few limited cases), while in Spanish, stress is always marked (even when there isn't an accent mark on a word, stress is completely predictable). "Ce" vs "cie" and "gi" vs "gie" can be arbitrary (e.g. "ciechi" = "blind people", "cechi" = "Czech people", with identical pronunciation; "scienza" could be written "scenza", just like "scemo" is, with identical pronunciatio of "sce" vs "scie" as /ʃe/). "Gli" as a word is pronounced with /ʎ/ but "glicine" is pronounced with /gl/. Not a big deal, but "ch" being /k/ tends to confuse people, since "ch" often indicates /tʃ/ in other languages, while Italian indicates it with "ci" or "ce" (or more specifically, with the lack of an "h" in the middle). The Spanish system is more intuitive for Englishs peakers.
 * There are more vowels: 7 vs the 5 of Spanish, although they go back to 5 in unstressed syllables. They are not typically distinguished in the orthography (except at the end of words or in some monosyllables, like "è" vs "sé"). Regional accents vary widely in the way they combine è/é and ò/ó, but despite that, if you pronounce them "like a foreigner", that will still be perceived as foreign. Depending on your native language, it may be easy to confuse "é" with "i", and "ó" with "u".

Difficulties of Spanish

 * The orthography is probably better than Italian's but it does have its own pitfalls: "je" and "ge" sound the same so you have to know which to use in a word ("jefe" vs "general", both have /x/); initial "h" is always silent and it's present in a lot more words than in Italian (which basically just has it in some forms of the verb "avere", while Spanish has words like "huevo", "horno" pronounced the same as *"uevo", *"orno"); you do have to learn the rules for when to put an accent mark or not, although the whole accent mark thing makes figuring out stress easier than in Italian. If you're learning a "seseo" accent, "ci"/"ce" and "si"/"se" have the same pronunciation, so you must learn how to write them; same with "yeismo", where "y" and "ll" will have the same sound.
 * The phonology is also trickier, with many allophones, like "b"/"v" sounding like /b/ or /β/ depending not on the spelling, but on the phonological context; similarly with /ɡ/ vs /ɣ/ and /d/ vs /ð/. Spanish has more unusual sounds (statistically over the world's languages) than Italian, with /θ/, if non-seseo, and /ð/ (although these aren't a problem for English speakers), and /x/, /ɣ/ (which can definitely be a problem for English speakers).
 * "Ser" and "estar" are used in a way that's very non-intuitive for English speakers, and sometimes arbitrary. While both verbs also exist in Italian, their distribution is more predictable, with "essere" being used for most things, and "stare" being relegated to continuous form "sto facendo" vs "estoy haciendo" (I am doing) and frozen form like "sto bene" (I'm well).
 * There are some unusual, but not very difficult, grammatical rules like having to use the article "lo" only in front of adjective used as noun ("lo bueno" means "the good", as in "the good for mankind", with "el bueno" meaning "the good [person] instead); another is having to use "a" for direct objects that are animate (people), but not "things".

Difficulties in common

 * Arbitrary genders; this is easy, many other IE languages have it, but still, you have to learn them, especially for words ending in consonant (in Spanish) or in -e (in Italian), which can easily be masculine or feminine. Nouns in -o and -a can have unexpected genders too ("la mano" feminine in both languages despite ending in -o, "l'astronauta"/"el astronauta" masculine despite ending in -a).
 * Complicated, often seemingly arbitrary, past tenses (both the simple and the composite past can hold surprises), even with verbs that are not very irregular. Actually irregular verbs are even worse, with widely different forms even in the various persons of simple present, and this type of irregular verbs contains a lot more elements than just English's "to be".

For now I'm tired of figuring out other ones...