How do I know when to spell a word with "r-" or "wr-"?
For example, (wr)ap and (r)ap, (wr)ing and (r)ing.
Both sets have the same R sound but different spellings.
Is there a way of working out which to use, or do I simply have to learn each word?
Learn English – How to know when to start a word with “r-” or “wr-“
orthography
Related Solutions
The answer, as with so many other such questions, is it depends.
How long ago did the word enter the English vocabulary? The longer ago, the less likely it is to retain the diacritics.
How frequently is the word used? The more frequently, the less likely it is to retain the diacritics.
Without the diacritics, does it look identical to a different English word, especially one that's pronounced differently? If yes, it's slightly more likely to keep the diacritics.
Is it a personal name? If yes, it will almost always keep the diacritics, at least nowadays. (Even just 20-30 years ago, personal names would be Anglicized to a much greater degree than they are now. For example, the conductor born in 1899 was Eugene Ormandy, not Jenő Ormándy, but the pianist born in 1953 is András Schiff, not Andrew Schiff.)
Is it a proper noun that is not a personal name? Then it really depends on the first three factors above, namely age, frequency, and conflict. Plus, there are place names that are translated into totally different words — for example, the difference between München and Munich is not just the umlaut. (This occurs in other languages, too: chances are, you don't call the countries "Suomi" or "Magyarország" in your native language, unless of course your native language happens to be Finnish or Hungarian, respectively.)
Are you writing for a publication that has a style guide about diacritics? Then follow that guide, even if it contradicts your experience or your dictionary.
The only way to settle this question is to look up each word in the dictionary (or encylopedia, if it's not the sort of proper noun that's listed in the dictionary). For the words in your example, here's what Dictionary.com had to say:
résumé; also resume, resumé
café; also cafe
naive; also naïve
Schrödinger
(no listing for Citroen or Citroën; Wikipedia only has the latter spelling)
In any case, don't get hung up on "but that's the wrong pronunciation!", and especially not on "but that's the wrong spelling!" Once a word has entered English vocabulary, it is slowly but surely assimilated, and at some point — same as with literally every other English word — its etymology becomes irrelevant. Its correct pronunciation will come from context and from the reader's knowledge, same as the rest of the words in the sentence.
A common use of hyphens is with words that form a compound adjective, such as, state-of-the-art, life-saving and so on.
There are, however, many rules when and when not to use hyphens. For example, check out a few from this link.
Rule 1. Generally, hyphenate two or more words when they come before a noun they modify and act as a single idea. This is called a compound adjective.
Examples: an off-campus apartment state-of-the-art design
When a compound adjective follows a noun, a hyphen may or may not be necessary.
Example: The apartment is off campus.
However, some established compound adjectives are always hyphenated. Double-check with a dictionary or online.
Example: The design is state-of-the-art.
Rule 2a. A hyphen is frequently required when forming original compound verbs for vivid writing, humor, or special situations.
Examples: The slacker video-gamed his way through life. Queen Victoria throne-sat for six decades.
Rule 2b. When writing out new, original, or unusual compound nouns, writers should hyphenate whenever doing so avoids confusion.
Examples: I changed my diet and became a no-meater. No-meater is too confusing without the hyphen.
The slacker was a video gamer. Video gamer is clear without a hyphen, although some writers might prefer to hyphenate it.
Writers using familiar compound verbs and nouns should consult a dictionary or look online to decide if these verbs and nouns should be hyphenated.
Rule 3. An often overlooked rule for hyphens: The adverb very and adverbs ending in -ly are not hyphenated.
Incorrect: the very-elegant watch
Incorrect: the finely-tuned watch
This rule applies only to adverbs. The following two sentences are correct because the -ly words are adjectives rather than adverbs:
Correct: the friendly-looking dog
Correct: a family-owned cafe
Here's another.
Best Answer
No. There is no way other than to learn them.
[Words starting with "wr-" are almost always native English words, from Germanic roots, rather than borrowings from French or Latin; but that does not really give you much help].