单因素加速条款（Single Trigger Acceleration Clause）和双因素加速条款（Double-Trigger Acceleration Clause）都是并购协议中常见的加速条款。这里的加速主要指的是加速推进对员工或高管的授予计划。单因素加速条款规定的是只要有一项规定事件——通常是收购或其他控制权变更发生，授予计划即加速推进；而双因素加速条款规定的是在规定的两项事件（一般是公司出售或收购，以及高管被无故解雇）发生后，加速推进授予计划。

单因素加速和双因素加速的英文释义分别如下：

单因素加速Single-trigger acceleration

Single-trigger acceleration refers to the partial or full acceleration of vesting of someone's options or stock based on the occurrence of a single event, i.e. that event is the “trigger” for acceleration. Double-trigger acceleration refers to acceleration based on the occurrence of two distinct events.

双因素加速Double-trigger acceleration

Double-trigger acceleration is when someone's stock or options can be vested ahead of schedule if there are two distinct triggering events. As a founder, your unvested equity might be accelerated if you sell the company and you're involuntarily fired soon after the sale.

以下为部分并购协议中的双语条款示例，供参考：

示例一：

Single Trigger Accelerated Vesting. As of the date of a Vesting CIC (regardless of whether or not Participant experiences a termination of employment), all unexpired equity-based awards (i.e. stock options, restricted stock awards, restricted stock unit awards, performance unit awards, etc.) then-held by Participant shall be fully vested to Participant; provided, however, that any equity-based award held by Participant which is deferred compensation under Section 409A of the Internal Revenue Code and the final Treasury Regulations thereunder (collectively, “Section 409A”), shall not be subject to accelerated vesting pursuant to this Section 3 unless the original terms of the equity-based award provide for such accelerated vesting. Any accelerated vesting per this Section 3 is subject to the provision and non-revocation of a release per Section 7.

单因素加速授予。截至授予CIC之日（无论参与者是否有经历过雇佣关系的中止），参与者届时持有的所有未到期股权奖励（即股票期权、限制性股票奖励、限制性股票单位奖励、绩效单位奖励等）应被全部授予参与者；但是如果参与者持有的任何股权奖励属于美国《国内税收法典》第409A条和该法典项下的最终财政部条例中规定的递延薪酬，则不应根据本第3条的规定进行加速授予，除非该等股权奖励的原始条款中有对此加速授予进行规定。本第3条规定的加速授予需受第7条中有关解除的提供和不可撤销的规定的约束。

示例二：

Single Trigger Acceleration Clause

单因素加速条款

Notwithstanding the foregoing, the vesting of the Unvested Shares shall accelerate such that the Repurchase Option in Section 3(a) shall lapse as to 100% of the Unvested Shares, effective as of immediately prior to consummation of a Change of Control. As used in this Agreement, “Change of Control” means (1) a sale of all or substantially all of the Company’s assets other than to an Excluded Entity (as defined below), (2) a merger, consolidation or other capital reorganization or business combination transaction of the Company with or into another corporation, limited liability company or other entity other than an Excluded Entity.

尽管有前述规定，未授予股份的授予进程仍应加速推进，以便使得所有未授予股份相关的、第3(a)条中所载的、在紧邻控制权变更完成之前有效的回购期权失效。在本协议中，“控制权变更”指（1）出售公司的全部或绝大部分资产，除非向除外实体（定义见下文）出售，（2）公司与其他企业、有限责任公司或者除外实体以外的其他实体进行兼并、新设合并或其他资本重组或企业合并交易。

示例三：

Double-Trigger Acceleration Clause

双因素加速条款

In the event that the Executive’s employment with the Company is terminated by the Company (or its successor) without Cause (as defined below) or by the Executive for Good Reason (as defined below) on account of or within twelve (12) months following the date of the consummation of a Change in Control (as defined below) (such period, the “Double-Trigger Period”), the vesting and exercisability of each of the Executive’s outstanding stock awards (including any stock options, restricted stock or other awards granted to the Executive by the Company) shall be automatically accelerated in full.

如果由于控制权变更（定义见下文）或者在控制权变更完成之日后十二（12）个月（该期限为“双因素触发期”）内，高管与公司之间的雇用关系被公司（或其继任人）无理由（定义见下文）中止，或者被高管以正当理由（定义见下文）中止，则高管尚未行权的每一项股权奖励（包括公司给予高管的任何股份期权、受限股份或其他奖励）的授予以及行权应全部自动加速推进。