必 means certainly, must and is a JLPT N3 kanji. It has 5 strokes and uses the heart radical (心).
Stroke order · 5 strokes
On'yomi (音読み)
ヒツ
Kun'yomi (訓読み)
かなら(ず)
Radical
心 · heart
Strokes
5
How to remember 必
A stroke cutting through the chest of the heart (心) — a vow etched into the chest: 'I will surely do it.' With 必ず, Japanese people give their word — and keep it too.