A condominium and an apartment are the same physical space, but the apartment is for rent. You buy a condominium.
“Condominium” is quite formal, too. Casually, most people will just call it a “condo.”
In England, people will call an apartment a “flat.” This is uncommon in Canada.
If you live in a house that is divided into two or more apartments, we call them “suites.” It’s pronounced the same as “sweets.” The lower suite is sometimes called the “basement suite” or the “garden suite.”