How do you use Greek a sentence?

You can't really "use Greek in a sentence" in the way you might use a word. Greek is a language, not a word.

However, you can write a sentence *in* Greek. For example:

Γεια σου! (Ya sou!) - This means "Hello!" in Greek.

Or, you could use a Greek word in a sentence:

The philosopher Plato argued that the soul is immortal.

Here, "Plato" is a Greek word, but the sentence itself is in English.

To use Greek effectively, you'd need to learn the language, which involves studying grammar, vocabulary, and pronunciation.

Is there a specific way you're hoping to "use Greek" in a sentence? Perhaps you have a sentence in mind and you want to translate it into Greek? I'm happy to help if you can provide me with more context.