IPA: /ˈdɪsɪplɪnd/
KK: /ˈdɪsəplɪnd/
Having self-control and the ability to follow rules or a set plan.
She is very disciplined in her studies, always completing her assignments on time.
Disciplined → It is formed from "disciplina" (from Latin, meaning instruction or training) and the suffix "-ed" (indicating a state or condition). The word "disciplined" refers to being in a state of training or instruction, often implying self-control and order.
Think of 'instruction' ('disciplina') that leads to a state of being controlled and orderly — that's what disciplined means.