KanjiJLPT N1
Vow

vow, swear, pledge

Mnemonic

You fold a sheet of parchment, inscribe solemn words on the inside, then seal it shut — this is your vow. The fold protects the words from all eyes but yours and the heavens. Only death can unfold that sacred paper.
Additional thoughts
Picture physically folding a paper with your oath written inside, pressing the crease hard to seal it forever. The act of folding makes the words permanent and hidden — a vow between you and the divine.
Quick recall
Fold sacred words into sealed parchment — a binding vow.

Details

The keyword for 誓 is vow. This kanji refers to a solemn, serious promise or pledge, often made before a higher authority or with deep personal conviction. It carries a sense of formality and gravity, as in swearing an oath or making a sacred commitment. The emphasis is on the binding and earnest nature of the declaration, distinguishing it from a casual promise.
On'yomi
せい
Kun'yomi
ちか.う