“正常闭合的”常见英文表达为 “normally closed”，常用于描述电路、阀门、开关等在无外力作用或正常状态下处于闭合状态的情况。
例如：
A normally closed switch remains closed until an external force acts on it.（正常闭合的开关在无外力作用时保持闭合状态。）
The valve is normally closed to prevent leakage.（这个阀门正常闭合以防止泄漏。 ）