Elasticity, Flexibility
noun
If you want the power to stop a bullet you need to have just the right amount of elasticity. Bullets go right through rigid things, but if the material is strong and has the right amount of flexibility, the bullet will bounce right off!
だんりょく
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
お肌の弾力が無くなってきているの。
The elasticity of my skin is disappearing.