WHOLE CHARACTER
定dìng
fixed; settled; to decide; to determine; surely; certainly; calm; steady
定 sets a roof over a foot planted still: fixed plans, decisions (决定), and 一定 'surely'.
ZDIC: 会意,从宀、从正. The bottom writes 正 as a fused variant — 一 over the foot piece 龰; shown as a visual aid, not the standalone word 正.
TOP: THE ROOF SIDE (ZDIC 从宀)
宀mián
covered house; shelter
Often called the roof component. Its dictionary meaning concerns a covered house; its role in this character is shown below.
In 定: top: the roof side (ZDIC 从宀) Shown with its documented or clearly limited role.
BOTTOM: THE WRITTEN VARIANT OF 正
Component group
Notice this part of the shape; it is not taught as a separate word in this lesson.
In 定: bottom: the written variant of 正 Shown with its documented or clearly limited role.