Secular

Secular in its most common meaning, means "outside religion". It can be used in a neutral sense, e.g. when at the end of the 17th century most sonatas were used in church services, a "secular" sonata meant nothing more than a sonata not used in a church service (without any connotation of the composer being religious or not). See Secularity as being relatively worldly.

On the other hand, secular can have the connotation of a dismissive conviction regarding religious matters: see secularism.

Secular can also indicate events recurring with a regularity of long periods (like centuries): see Secularity as relatively long duration and Secular trend.