Stratify vs Undefined - What's the difference?

As a verb stratify

is to become separated out into distinct layers or strata.

lacking a definition or value.

(en-verb)

To become separated out into distinct layers or strata.

In this cut you can see how the sedimentary rock layers have been clearly stratified .

Even without a pronounced social class system, people in a large society tend to stratify .

To separate out into distinct layers or strata.

(wikipedia undefined) (-)

Lacking a definition or value.

(mathematics, computing) That does not have a meaning and is thus not assigned an interpretation.

The result of division by zero is undefined .

* defined