xīn heart; mind

Forms

• 忄 left — Compressed upright form used on the left side, as in 忆.
• ⺗ bottom — Flattened form used under another component, as in 恭.

Characters that use it as a component

必忌忍志忘忠态沁

Characters filed under it as a radical

Kangxi radical no.61 · 4strokes — 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.

心必忆忌忍志忘忙