# π-system and monotone class

##### New Member
Assume P is a π-system (that is, P is closed under finite intersections) and M is monotone class (that is M is a non-empty collection of subsets of Ω closed under monotone limits).

Show that P⊂M does not imply σ(P)⊂M.

#### BGM

##### TS Contributor
The complement is not necessary in the monotone class?