Το λεωφορείο άργησε, έτσι πήγα με το μετρό.

Το is the definite article meaning the.

Both λεωφορείο (bus) and μετρό (metro/subway) are neuter singular nouns, and the neuter singular definite article is το.

So:

• το λεωφορείο = the bus
• το μετρό = the metro

Greek uses the definite article very often, sometimes more often than English does.

They are both neuter singular nouns, which is why they go with το.

A learner will often notice that many neuter nouns in Greek end in:

• -ο
• -ι
• -μα

Here:

• λεωφορείο ends in -ο
• μετρό also behaves as a neuter noun

That is why the sentence uses το λεωφορείο and το μετρό.

Άργησε is the aorist form of αργώ.

In this sentence, it means something like:

• was late
• came late
• was delayed

So Το λεωφορείο άργησε means the bus did not come on time.

Depending on context, English might translate it a little differently, but the basic idea is that the bus was late.

Greek often uses the aorist to describe a single completed event in the past.

Here, the speaker is talking about one specific situation:

• the bus was late
• as a result, I took the metro

So άργησε fits well because it presents the lateness as a complete event.

If you used the imperfect instead, it could sound more like an ongoing or repeated situation, which is not the main point here.

Here έτσι means so, therefore, or as a result.

It connects the two parts:

• Το λεωφορείο άργησε
• έτσι πήγα με το μετρό

So the meaning is:

• the bus was late, so I went by metro

In other contexts, έτσι can also mean like this or this way, but here it clearly has the meaning of so / therefore.

Because Greek usually does not need subject pronouns when the verb ending already shows who the subject is.

Πήγα means I went.
The ending tells you it is first person singular.

So Greek normally says:

• πήγα = I went

You could say εγώ πήγα, but that adds emphasis, something like:

• I went
• I was the one who went

In a neutral sentence, leaving out εγώ is completely normal.

Πήγα is the aorist of πηγαίνω (to go).

It means I went as a completed action in the past.

That works well here because the speaker is describing one finished decision/action:

• the bus was late
• so I went by metro

If the speaker wanted to express an ongoing or habitual action, a different tense would be used.

Με usually means with, but in sentences about transportation it often means by.

So:

• πήγα με το μετρό = I went by metro
• literally, something like I went with the metro

This is a very common Greek pattern:

• με το λεωφορείο = by bus
• με το τρένο = by train
• με το αυτοκίνητο = by car

So με + article + means of transport is a normal way to say by ....

Greek very often uses the article with means of transport.

So με το μετρό is the normal, natural way to say by metro.

English often drops the article in expressions like:

• by bus
• by train
• by metro

Greek usually does not do that in the same way. Using το here sounds natural and standard.

The comma separates two connected clauses:

• Το λεωφορείο άργησε
• έτσι πήγα με το μετρό

It helps show that the second clause is the result of the first one.

In English, this is similar to writing:

• The bus was late, so I went by metro.

So the comma is doing the same kind of job here: it marks a pause and clarifies the relationship between the two ideas.

Yes. Greek word order is fairly flexible, although some versions sound more natural than others depending on emphasis.

The original sentence:

• Το λεωφορείο άργησε, έτσι πήγα με το μετρό.

is very natural.

You could also hear things like:

• Άργησε το λεωφορείο, έτσι πήγα με το μετρό.
• Έτσι πήγα με το μετρό, γιατί το λεωφορείο άργησε.

But these versions shift the focus slightly.

The original version is a straightforward, neutral way to say it.

The accent marks show where the stress goes.

• λεωφορείο → stress on -ρεί-
• άργησε → stress on άρ-
• έτσι → stress on έ-
• πήγα → stress on πή-
• μετρό → stress on the final -τρό

So the stressed parts are:

• λεωφορείο
• άργησε
• έτσι
• πήγα
• μετρό

Paying attention to stress is important in Greek because it is part of correct pronunciation.

It can cover both ideas, depending on context.

Most naturally in this sentence, English speakers will understand it as:

• The bus was late

But the Greek verb αργώ can also suggest:

• something came late
• something was delayed

So Το λεωφορείο άργησε can imply that the bus did not show up when expected, which is why the speaker chose another means of transport.