I have often heard of "periodic" sentences, but never saw
the difinition before:
period


from Gk. periodos “going around, course”
hirmos
ambitus, circumductum, continuatio, conclusio, hirmus
long loose

The periodic sentence, characterized by the suspension of the completion of sense until its end. This has been more possible and favored in Greek and Latin, languages already favoring the end position for the verb, but has been approximated in uninflected languages such as English.
Example
Note the long delay prior to the occurrence of the sentence's main verb ("sing"):
Of man's first disobedience and the fruit
Of that forbidden tree, whose mortal taste
Brought death into the world, and all our woe,
With loss of Eden, till one greater Man
Restore us, and regain the blissful seat,
Sing Heav'nly Muse...

—John Milton, Paradise Lost