linking word after 'to depend on'

[Irene29]

Hi,

Is it necessary to put any linking word e.g. 'that' after the verb 'to depend on' in the following sentence:
'It depends on if it is interesting or not...'
By the way, is it true that 'whether' is commonly used in formal speech and 'if' in informal one?

Thanks in advance!

[Beeesneees]

I wouldn't use 'if' in that example, even informally. I know that some people would though. You definitely ought to stick with 'whether' in a formal setting, though.

I'd use one of these variations:

'It depends on whether it is interesting or not'
'It depends whether it is interesting or not.'
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