What is Aptitude?

Legal Definition
An aptitude is a component of a competence to do a certain kind of work at a certain level. Outstanding aptitude can be considered "talent".An aptitudes may be physical or mental. Aptitude is inborn potential to do certain kinds of work whether developed or undeveloped. Ability is developed knowledge, understanding, learned or acquired abilities (skills) or attitude. The innate nature of aptitude is in contrast to skills and achievement, which represent knowledge or ability that is gained through learning.
According to Gladwell (2008) and Colvin (2008) often it is difficult to set apart an outstanding performance merely because of talent or simply because of hard training. Talented people as rule show high results immediately in few kinds of activity, but often only in single direction or genre.
-- Wikipedia
Legal Definition
Having an ability to learn new skills. Interest in what is being taught or trained is important.