Verb

(refin)

To reduce to a fine, unmixed, or pure state; to free from impurities; to free from dross or alloy; to separate from extraneous matter; to purify

* {{quote-magazine, date=2013-08-03, volume=408, issue=8847, magazine=(The Economist)

, title= Yesterday’s fuel , passage=The dawn of the oil age was fairly recent. Although the stuff was used to waterproof boats in the Middle East 6,000 years ago, extracting it in earnest began only in 1859 after an oil strike in Pennsylvania.

To purify from what is gross, coarse, vulgar, inelegant, low, and the like; to make elegant or excellent; to polish.

To become pure; to be cleared of feculent matter.

To improve in accuracy, delicacy, or excellence.

To affect nicety or subtlety in thought or language.

Verb

(en-verb)

To make simpler, either by reducing in complexity, reducing to component parts, or making easier to understand.

To become simpler.

* 2006 , Karen Oslund, “Reading Backwards: Language Politics and Cultural Identity in Nineteenth-Century Scandinavia”, in David L. Hoyt and Karen Oslund (editors), The Study of Language and the Politics of Community in Global Context , Lexington Books, ISBN 978-0-7391-0955-7, page 126:

Thus, throughout the nineteenth century, linguists generally held that more grammatically complex languages were older and that languages tended to simplify over time—the four grammatical cases of German as contrasted with the seven of Latin, for example.