贞 zhēn chaste
Made up of [贝 bèi shell; precious; cowrie shell radical 154, 卜 bǔ divination; prophesy radical 25]Made with 6 strokes.
The radical 'shell' suggests something intact and enclosed. Derivation may be from reading the future with a ritual vessel
Ancient small seal form 
Related characters
Also uses 贝 bèi component: 厕 cè (toilet) 贵 guì (precious) 贫 pín (poor) 赏 shǎng (to hand down) 贴 tiē (to stick) 员 yuán (person) 则 zé (conjunction used to express contrast with a previous sentence or clause)
Also uses 卜 bǔ component: 处 chù (place) 咎 jiù (fault) 外 wài (outside) 占 zhān (to observe) 桌 zhuō (table)