◇ Noun Clause
名詞子句
if 當作「是否」之意時，常放在句中，前面常出現的動詞有 wonder、know、decide、ask、doubt 等，且可以與 whether (or not) 互換使用。if 作「是否」講時所領導的子句也被稱之為「名詞子句」，是一種從屬子句。這個子句可以被代名詞替換。例如 Investors will have to decide if WeWork's size and flexibility are enough to...，這句的 if 子句可以直接被代名詞 it 或 that 替換，變成 Investors will have to decide that/ it。
Example：
1. Jemma was merely questioning whether we have the money to fund such a project.
Jemma 只是想問問我有沒有錢來支柱這樣一個專案計畫。
2. We need to consider if the disadvantages of the plan outweigh the advantages.
我們必須考慮這個計畫的壞處是否大於好處。
3. I asked him if he had done it all himself or if someone had helped him.
我問他是否那都是他自己獨自完成的。