"An" is used if and only if the next word starts with a vowel sound. In some dialects, the "h" is silent, so you would say (and spell) "an historic." In American English (which I think Duolingo is geared toward), the "h" should be pronounced, and so you should always say and spell "a historic."
Forgive the essay... This 'a/an historic' debate is not a UK/US difference. It's just an old school language rule that most English speakers either ignore or don't know about.
Yes, some accents (notably some British ones) drop 'h's when they speak, and would naturally use 'an' rather than 'a' in those cases, but this is not correct English, because it is incorrect to drop the 'h' in the first place. Eg. Correct (verbally and written): a horse, a hot dog, a hospital... Incorrect (but not uncommon verbally): an 'orse, an 'ot dog, an 'ospital...
Essentially, in English, the correct time to use 'an' is where is it needed to prevent an awkward glottal stop, i.e. before a vowel sound, and the correct time to use 'a' is everywhere else, i.e. before a consonant sound. Eg. an elephant, an avocado, an hour, an honour.... a dog, a house, a university...
That's the rule all English speakers tend to follow - if it sounds like a consonant when you say it, use 'a', if it sound like a vowel, use 'an'.
BUT, there is an (archaic) exception, which states that when a word begins with 'h' and is stressed on the second syllable, you use 'an'. Presumably this reflects how words used to be pronounced back in the day, but who knows. Eg. an historic, an heroic, an horrendous... (yes Annwenn I just stole all your examples)
HOWEVER, as I said, most people don't know or don't care about that rule, and just keep it simple. You're certainly not wrong if you say 'an historic' but nobody reasonable will complain if you use 'a historic', as the vast majority would!
Not to wander too far from Spanish, but I was taught that during WWII (or maybe WWI), when we got news about the European front from the British, our journalists picked up their very British "an historic event", as they don't pronounce the "h" over there. So now that's the one "h" word in American English that people (esp. journalists) precede with "an". It drives me crazy.
What words in American English start with silent H's that aren't borrowed from other languages? I think it's just about whether the word starts with a vowel sound.
Do you have any other examples of words that - start with the letter H - start with an /h/ sound - have the stress on the second syllable - anyone would actually say 'an' in front of ?
JB, you & others are right about journalists picking up the Brit pronunciation & misusing the article "a" in Am. Eng. newscasts. Journalism & Eng. were my degree majors, & just because an uninformed public "accepts" their error, because they don't know the rule governing it, doesn't make it correct. The vowel sound dictates the use of "an," a "hard 'h' sound" requires "a," as in horse, hat, hotel, etc. Trust me; many journalists are NOT experts in grammar, but just read teleprompters. To be correct in Spanish, we must accept their rules, & that applies in reverse. It is NOT "street" or "ignorant" speech to say A historic day; it follows the rule of American English. Also, no one I know says "herb" with a hard "h" sound except for the man's name "Herb," otherwise it's pronounced "'erb."
Aw, I really wanted your explanation to be true. This chart seems not to reflect the notion though. https://books.google.com/ngrams/graph?content=an+historic%2Ca+historic&year_start=1900&year_end=2008&corpus=17&smoothing=3&share=&direct_url=t1%3B%2Can%20historic%3B%2Cc0%3B.t1%3B%2Ca%20historic%3B%2Cc0 Granted, I don't know exactly what content Google sifts through (just books?), but it would be really weird if the phenomenon just hit journalists and stopped there.
Merriam-Webster says 'A' historic is up to 4 times more common than 'AN' historic in US English and that 'AN' is used commonly enough to be considered correct.
Majority is 'A' historic as the 'h' is pronunced unlike in the words 'hono(u)r' and 'hour' where it is not pronounced.
Go with 'A' historoc and accept that 'AN' is being allowed through as a typo.
Side note... I will always say herb vs 'erb. 'erb sounds too much like a child learning to speak that still says 'free' instead of 'three'.
Duo Lingo wants to hear Today is a historic day; hoy = today. In many cases, you can translate it using "this" or "it" instead of "today" if the rest of the sentence makes it clear that you're talking about a day, but it's hard to make general rules. In this particular case, it is my opinion that "This is a historic day" is valid. From what I can think of, "it" is more commonly used, but the best pattern I can come up with is that "it" is used when you're specifying which day is today, especially either by the date or by something that can be used to identify the date or else is tied with the specific date. Examples: "It's my birthday!" "It's Friday." "It's November 5th." "It's Valentine's Day!" "It's National Sundae Day!" "It's the first day of classes." Whereas "this" is used when saying something about today that is not being identified specifically with the date. Examples: "This is the worst day of my life." "This is the kind of day where schools usually close." "This is the day that I will [verb]!" But sometimes "it" is better even when it has nothing to do with the date: "It's a great day for golf!" And sometimes people use "it's" but then end the sentence with "today" as in, "It's a hot day today." So it's hard to come up with a general rule, besides the fact that in every case (as far as I can think of), "today" works as well as anything. (Examples: "Today is my birthday!" "Today is a great day for golf!" "Today is the worst day of my life.")
"Today is an historic day" is correct. As in "hotel", "honour", "honorarium", "hour" the "h" is not pronounced, and the article is "an", although usage often has the "h" in hotel sounded. The comment concerning the number of syllables in the word is valid, but only sometimes. (In English there always unreasonable exceptions, and reasonable people might just have to be equally unreasonable.)