十個特別的wh字3: whereby

whereby=by which way or method:此，從而；藉以 

They've set up a plan whereby you can spread the cost over a period. 他們已經制訂了這樣一個計劃，允許在一段時間內分期付款。

We need to devise some sort of system whereby people can liaise with each other. 我們需要設計一套辦法，人們能夠藉以互相保持聯絡。

(注: thereby是近似的字,意思是as a result of this action[因此，由此；從而], 例:

Diets that are high in saturated fat and cholesterol tend to clog up our arteries, thereby reducing the blood flow to our hearts and brains.
高飽和脂肪和高膽固醇的飲食容易阻塞我們的動脈，從而減少向心臟和大腦的供血。)