Semantic Change

Old definitions: 
Lean: thin, emaciated

Novice: a member of a religious order who has not taken vows yet
Revolutionary: someone who favours overthrowing the government
Lewd: not having an official position in the church.

Modern definitions:

Lean: especially healthily so; having no superfluous fat.

Novice: a person new to and inexperienced in a job or situation.
Revolutionary: involving or causing a complete or dramatic change.
Lewd: crude and offensive in a sexual way.

The word "Lean" originated from the borrowing of the German lexis, hlinian; related to Dutch leunen and Germanlehnen, from an Indo-European root shared by Latin inclinare and Greek klinein. This semantic change of this word has shifted the definition, meaning that the use of the word within conversations and lexis use has fluctuated over the years.

"Novice" originated as Middle English: from Old French, from late Latin novicius, from novus ‘new’. The new definition makes more logical sense as it relates the original word's meaning; this semantic change is not as strong.

"Revolutionary" used to be referred with a political definition, however the change in semantics has generalised and has weakened the word to describe a situation as opposed to describing a person.

The definition of the word "Lewd" has shifted; the comparison of the old definition has completely changed semantically. The modern definition of the Old English word has changed to an euphemism to talk about a less pleasant subject through an informal, jokey manner.