Void 同Avoid有咩分別??

實用性的意思
void = 取消/癈除
avoid = 避免/免受

void動詞通常用於取消一樣已是事實但權力上可以消除的行動
avoid動詞通常用於作為提醒或理由去避免一樣可能會發生的事情

所以然字典的詞義好像一樣，但通常不會在同一樣情況上可以共通的。簡單地記住void是你主動做去消除一樣已經出現的事情，avoid是主動地不想某一事情出現。

你的例句意思是
假如其中一方可以選擇宣告那事作(或合約)癈以作為逃避(它/他)在合約中的責任…(這句應該有前一句或之後交代為何作這假設或後果如何)

VOID (verb)
作廢, 使無效
To void something (such as contract, agreement) means to state officially that it has no legal effect.

AVOID (verb)
~ make legally void 撤銷 (法律), 躲避
Avoid a plea.

To void a contract is to actively acknowledge its existence while disputing its legitimacy. That is, when one argues that the contract was illegitimate as the result of fraud (欺騙) or noncompliance (不服從);

To avoid a contract is to ignore it. The contract exists, but there is a reason to fail to comply (遵從) with the terms of the contract. This is usually due to a breach (破壞, 違反) of the contract or other reason.

For example, a child who is under the age of capacity may disavow (否認) a contract and avoid her obligations under it because she lacks the legal capacity to enter into a contract.

你的句子:
If one of the parties may choose to declare it void (adj. 無效) and avoid (verb 撤銷) its obligations (義務,責任) under the contract.

Avoid 其他意思:
AVOID (verb) 避免, 躲避; 撤銷
If you avoid something, you take action to prevent it from happening to you.
If you avoid doing something, you make sure you do not do it.