In which cases do you say "oxide" when naming a molecule? Based on the names of following molecules I got quite confused about the correct nomenclature:


$\ce{NaHCO3}$
$\ce{K2SiO3}$
$\ce{PbCrO4}$


In none of the above molecule names you ever say "oxide" although there is a oxygen atom. Why? What is the applied rule for the nomenclature? In which cases do you actually say the word "oxide" in the name of the molecule?
The naming nomenclature for inorganic molecules is confusing, but if you are studying chemistry then you just have to grit your teeth and learn.

First there are household names, common names and chemical names. Vinegar, acetic acid, and ethanoic acid are talking about the same molecule. We say water, but aqueous solutions. $\ce{SiO2}$ is silicon dioxide to a chemist, but quartz to a geologist. The list could go on and on...

In general an oxide is compound which has just some element, X, and oxygen in some combination - ${\text{X}_m\text{O}_n}$

Some anion combinations get a name. 


$\ce{CO3^{2-}}$ is carbonate
$\ce{SiO3^{2-}}$ is metasilicate
$\ce{CrO4^{2-}}$ is chromate