Learn Hardcore Russian: Машина осторожно едет по дороге. - The car is driving carefully on the road.

Russian does not have articles like “the” or “a.” Nouns appear without them, and definiteness or indefiniteness is understood from context. If you need to emphasize “this car” or “that car,” you add demonstratives: эта машина (this car), та машина (that car).

What case is дороге in, and how do I know it’s not Prepositional?

дороге is the dative singular of дорога. You know it’s dative (not prepositional) because the preposition по (when it means “along,” “through,” “over”) always takes the dative for motion along a surface. The prepositional case is used after в or на to indicate location (e.g. на дороге = “on the road,” where it’s static).

Why is the preposition по used here instead of на or в?

по
- dative expresses movement along or across something (“along the road,” “across the field”).
на
- prepositional would mean location on the road (e.g. “The car is stopped on the road”).
в
- accusative would mean going into something (“drive into the garage”).
  Since we want “the car is driving along the road,” we choose по дороге.

What’s the difference between ехать (едет) and ездить (ездит), and why is едет correct here?

ехать is an imperfective, unidirectional verb: one-way or ongoing travel (“to go by vehicle in one direction”). Its 3rd-person form is едет (“is going/driving”).
ездить is an imperfective, multidirectional or habitual verb: regular trips or round-trips (“to go/ride often or back and forth”).
Here we describe the car’s single ongoing motion right now, so we use едет.

What part of speech is осторожно, and why not use осторожный?

осторожно is an adverb answering “how?” It modifies the verb едет (“drives how? carefully”).
осторожный is an adjective, which would describe a noun (“a careful driver” = осторожный водитель). Adjectives cannot directly modify verbs, so to say “carefully” you need the adverb осторожно.

How is the adverb осторожно formed from the adjective осторожный?

You take the adjective осторожный and replace the ending -ный with the adverbial suffix -но, yielding осторожно. Many Russian adverbs are formed this way (e.g. тихий → тихо, быстрый → быстро).

How do I pronounce “Машина осторожно едет по дороге”? Where are the stresses, and is that е in едет pronounced /ye/ or /yo/?

Recommended phonetic:
• [mɐˈʂinə ɐˈstorəʐnə ˈjedʲɪt pə dɐˈroɡʲe]
Stresses:
• ма-ШИ́-на
• ос-то-РО́Ж-но
• Е́-дет
• до-ро-ГЕ́
The е in едет is pronounced /ye/ (not /yo/). Russian spells ехать with an е, so you say [je-], even though ё would be /jo/.

What person and number is едет, and what tense/aspect is it?

едет is third person singular, present tense of the imperfective verb ехать. It means “(he/she/it) is driving” or “goes (by vehicle)” right now, emphasizing the ongoing action.

Why use машина instead of автомобиль for “car”? Are they different?

They are synonyms:
• машина is the everyday, colloquial word for “car.”
• автомобиль is more formal or technical (“automobile”), borrowed from French/Latin.
In normal speech you’ll hear машина, though both are correct.