pledge/ plεʤ /

1.noun [c] 
(promise) 誓言

2.vt.[+money] [ support] [ help] 
(promise) 发誓

to pledge that...
保证…
to pledge to do sth
保证做某事
to pledge sb to secrecy
叫某人发誓保密
to pledge o.s. to sth
保证某事