'Dear' used to mean 'expensive' in English too (in fact, modern dictionaries still mention this meaning, although it's definitely no longer widespread). This is quite a common meaning shift: people or things you love and cherish are considered valuable and compared with things that have a high price.
'Road' is a completely different word, and forms of this word are formed differently. The main form, nominative case, is доро́га. Only one form, instrumental case, happens to coincide with 'dear', while most of them can't be confused. Also, they can only be confused in writing, but not in speech: they differ in stress, доро́гой 'with road' vs. дорого́й 'dear, expensive'.
Yes, you're right. Дорога́ would indeed be the feminine form of mean 'dear', and it can indeed be confused with доро́га. I just didn't think of this form.
It is the same in Polish. English has some very strange homonyms too, but we have a lot of ways to spell the same word, so they are typically spelled different. For example, "great" and "grate." How many things can that sound mean? Your great grandma is great a grating cheese with the grater! Almost sounds Trumpian.
дорога and дорого have incognate disparate origins. [Дорога road, path, way, from Proto-Slavic dorga · https://en.wiktionary.org/wiki/Reconstruction:Proto-Slavic/dorga] [Дорого dear, precious, vital, from Proto-Slavic dorgъ · https://en.wiktionary.org/wiki/Reconstruction:Proto-Slavic/dorgъ]
Are you sure you’re not confusing дорого́й ‘dear, expensive’ with до́брый ‘kind, good’?
I don’t think дорого́й can be translated as ‘kind’, neither about people nor about cats.
Probably no. I'm not good at etymology, but etymological dictionaries don't even mention this as 'unlikely', so there must be some obvious reason why it can't be cognate.
By the way, -оро- in дорогой is a reflex on *or in Proto-Slavic (Wikipedia article here). Such reflexes are called «полногла́сие» 'pleophony', and they're opposed to «неполногла́сие» 'non-pleophony' in «драго́й». «Драго́й» is actually a borrowing from Old Church Slavonic and therefore it shows how these words were developed in Old Bulgarian. The word «драго́й» itself is not used often (except if you want to give your text a flavour of ye olde times back when Old Church Slavonic was a literary language), but «драгоце́нный» 'precious' is used often (драгоце́нный = драго́й + це́нный). Russian has quite a lot of Old Church Slavonic borrowings, so you'll be seeing such pairs a lot.
In Russian скупо́й means 'not generous, stingy, mean', and it's only used about people (and it's not a polite thing to say) :D
English words, dear, as in precious; tear as in rip, peel, flay, slice, pluck, skin; and derma as in skin, endoderm, mesoderm, ectoderm & etc., share the same origin as slavic words дорого, драго. Humanity and other sentient beings appreciate the dearness of preserving one's own protective skin intact. Cognitive humans have hunted and harvested animal, herbal and mineral skin to preserve and enhance their own vital skin since prehistoric time. Humanity well comprehends the consequence of an organism losing its own skin. Life's greatest expense born is losing one's skin. Dearest derma, once lost, life itself soon follows, mercifully. https://en.wiktionary.org/wiki/Reconstruction:Proto-Slavic/dorgъ https://en.wiktionary.org/wiki/Reconstruction:Proto-Indo-European/der-
I kinda coded it in my own native tongue (Turkish), as in the Russian course I went, the letter writing started with eg "Дорогая Элина", which is "Dear Elina" for English, but the closest thing we have is like "Değerli Elina", or "Kıymetli Elina" (literally: "Valuable Elina", one modern, the other a little out-of-date) a little bit rarely used letter starting-mainly we use "Sevgili Elina", which literally means "Loving Elina" in the sense of the German word "Liebe". Long story short, I wrote "valuable person", but it wasn't accepted. I think it kinda merges the aspects of "dear" and "valuable", what do you think? My next question...why wasn't it accepted?
I find it really odd that, although emphasis is placed on the 2nd syllable by native-speakers, that syllable is pronounced as an unstressed syllable - with the "a" sound instead of the "o" sound. https://forvo.com/word/%D1%87%D0%B5%D0%BB%D0%BE%D0%B2%D0%B5%D0%BA/#ru