Ο γείτονας έγινε πλούσιος.

The neighbor became rich.

Breakdown of Ο γείτονας έγινε πλούσιος.

• ο γείτονας: the male neighbor
• γίνομαι: to become
• πλούσιος: rich

Questions & Answers about Ο γείτονας έγινε πλούσιος.

What does ο mean here?

Ο is the masculine singular nominative form of the.

It matches γείτονας, which is a masculine singular noun here, so ο γείτονας means the neighbor. In this sentence, ο γείτονας is the subject.

Why is it γείτονας and not γείτονα?

Because γείτονας is the nominative singular form, and the subject of the sentence has to be in the nominative.

Here, the neighbor is the one doing the action of becoming, so Greek uses ο γείτονας.
By contrast, γείτονα is typically the accusative singular, as in:

Βλέπω τον γείτονα. = I see the neighbor.

What tense is έγινε?

Έγινε is the aorist form of γίνομαι.

In this sentence, it means became or got:
Ο γείτονας έγινε πλούσιος. = The neighbor became rich / got rich.

The aorist is the normal Greek past tense for a completed event.

Why is the verb έγινε and not something that looks more like γίνομαι?