Selenium doesn't have a single oxidation state. Like many elements, it can have several depending on the compound it's in. Here are some common ones:

* -2: This is the most common oxidation state, found in selenides like sodium selenide (Na₂Se).

* +2: Found in compounds like selenium dioxide (SeO₂).

* +4: Found in selenous acid (H₂SeO₃).

* +6: Found in selenic acid (H₂SeO₄).

It's important to remember that the oxidation state of an element can vary based on the specific compound it's part of.