Breakdown of Он всегда приходит на работу вовремя.
он
he / it (for a masculine noun) / it (for a neuter noun)
работа
work, job
всегда
always
на
on, at / by (transport) / to (a place) / to (in answer to)
Questions & Answers about Он всегда приходит на работу вовремя.
Why use приходит here instead of придёт or приезжает?
приходит is the imperfective form of the verb meaning "to arrive (on foot)." We use the imperfective aspect here because the word всегда (always) shows that this is a repeated, habitual action. If it were a one-time completed arrival, you would use a perfective form. Also, going to work is generally treated as an "on foot" arrival in Russian unless you specifically want to emphasize the mode of transport, in which case you could use приезжает (arrives by vehicle).
What exactly does the prefix при- add to the basic verb of motion?
The prefix при- adds the meaning of "arrival" or "reaching a destination." While the basic verb ходить means walking around or making round trips, adding при- changes the focus completely to the moment of showing up or arriving at a place.
The English translation says "arrives at work". Why is it на работу (accusative) instead of на работе (prepositional)?
Prefixed verbs of motion still act like verbs of motion! Because he is moving toward a destination, you must use the accusative case to show direction ("to where?"). Even though English says "arrives at", Russian thinks of it as "arrives to work". If you used the prepositional на работе, it would mean the physical act of arriving happened while he was already located at work.
Is the word вовремя (on time) just the preposition в plus the word (time)?