assurance
词根词缀：
assure v. 保证；确信
as 加强 + sure 肯定 → 一再肯定 → 确信
assurance n. 保证
as 表加强 + sur 肯定；安全 + ance 表状态 → 保证
assuredly adv. 无疑地
as 表加强 + sur 肯定；安全 + ed 表形容词 + ly …地 → 无疑地
insure v. 保险；保证
in 使… + sur 肯定；安全 + e → 使安全 → 保险
insurance n. 保险
in 使… + sur 肯定；安全 + ance，insure 的名词 → 保险
reassure v. 使确信
re 一再 + assure 保证；确信 → 使确信
surety n. 保证；保证人
sur 肯定；安全 + ety 表状态 → 保证；保证人
数据来源：新东方英语词汇速记大全
相关例句：
He would like an assurance that other forces will not move into the territory that his forces vacate
他想确保其他势力不会在他的军队撤离后进入这个地区。
The first area of interest between quality assurance and IT security is related to access control.
质量保证和IT安全性之间的第一个关注领域与访问控制有关。
They had given an absolute assurance that it would be kept secret.
他们信誓旦旦地保证将对此绝对保密。
He has a life assurance.
他投保了人寿保险。
She said 'hi' with the blithe assurance of someone who knew how much she'd been missed.
她高兴地说了声“嗨”，好像确信大家非常想念她似的。
Test and quality assurance.
测试和质量保证。