#6 Writing Definition

1. dis·ci·pline/ˈdisəplin/

noun

•  training to act in accordance with rules; drill: military discipline.
•  activity, exercise, or a regimen that develops or improves a skill; training: A daily stint at the typewriter is excellent discipline for a writer.
•  punishment inflicted by way of correction and training.
•  the rigor or training effect of experience, adversity, etc.: the harsh discipline of poverty.
•   behavior in accord with rules of conduct; behavior and order maintained by training and control: good discipline in an army. 

verb(used with object)

• to train by instruction and exercise; drill.
• to bring to a state of order and obedience by training and control.
• to punish or penalize in order to train and control; correct; chastise.

Source: http://dictionary.reference.com/browse/discipline

Presently, the word discipline involves teaching (not punishment). A training to act with accordance with the rules or by way of correction and behavior. An exercise that develops or improves a skill. At this point, it is training by instruction and exercise.