lifeline

noun
1
a line or rope thrown to rescue somebody who is in difficulty in the water
طناب نجات, ریسمان نجات
2
a line attached to somebody who goes deep under the sea, for sending signals to the surface
طناب نجات, طناب ایمنی
3
something that is very important for somebody and that they depend on
تکیه‌گاه, نجات‌بخش, راه نجات, وسیله‌ی حیاتی, کمک حیاتی
The extra payments are a lifeline for most single mothers.
He threw me a lifeline when he offered me a job.