のなら: emphasis or hearsay? What is the additional nuance in meaning when is inserted before ? For example: > () In the Tobira Gateway to Advanced Japanese (p. 69) it says > occurs before when the supposition is based on what the speaker has heard from someone or learned from the situation. However, other websites such as < and < explain that adds emphasis.

This is an explanatory-. Roughly speaking, it adds the nuance of "(if) ... is the case" or "(if) it's that ...". This is usually optional, but it indicates the conditional is something that does matter now.

You can use to seek clarification in an interrogative sentence (see this). This connotation is preserved when it's used with . If you understand the difference between "" and "", you know the difference between and , too. This type of is often used with external information, but is not a hearsay marker _per se_. It's not a plain emphasis marker that turns "if Tom comes" to "if Tom does come", either.

With that said, it's okay to add unconditionally most of the time in conversations. The difference is usually very small. tends not to be used with "generic fact" or "purely hypothetical" conditionals that have little to do with the current situation at hand (e.g., , , , ...).