Component (a building block) — not the same thing as a radical or a sound component. · 3strokes
字宁它宅宇守安宋
Kangxi radical no.40 · 3strokes — The 214 Kangxi radicals
Filed under it in a dictionary. That is a lookup convention — it does not mean it is the only part the character is built from.
宁它宅宇守安宋完