"Αυτό είναι το σπίτι μου."

Translation: This is my house.

[J.C.M.H.]

Does in Modern Greek the word οίκος exist?

[troll1995]

There is η οικία which is (very) formal for house and ο οίκος which is the word used for an important family, a dynasty or a company or a social welfare institution.

[J.C.M.H.]

Thank you for the answer. Then, the general word for "house" is σπίτι?

[troll1995]

The everyday, general word for house is σπίτι, yes, unless you talk formally. For example, in the news, you will hear Η συνάντηση θα λάβει χώρα στην οικία του προέδρου=The meeting will be held at the president's house, and not στο σπίτι του προέδρου.
Just because it came up in my mind: Σπίτι and hospital share the same ancestor "hospitium" from Latin.

[jss.___]

Good mnemonic device: hospital - house of the sick.

[Marva441926]

So σπίτι is a loanword from Latin? When did it enter the Greek language?

[troll1995]

It entered the Greek language in koine Greek, during the roman occupation. In the beginning it was οσπίτιον.

[J.C.M.H.]

OK, thanks!

[jasonalcant]

So, when you have guests in your σπίτι, show them hospitality.

[Lng52-._]

Do "home" and "house" = "σπίτι"?

[D_..]

Yes!