If necessary, you can contact me on the weekend.

Some information of the subordinate clause is omitted.

How does "if+ adjective" work? Is there a rule?

1 Answer 1


You can understand this as "If it is necessary,..." With the pronoun implied by context. It's normally only suitable for "telegraphese" or rather unnaturally shortened expressions.

If ready, you can begin. ("If you are ready,..." or "If it is ready,..." according to context)

When hot, add the tea. ("When it is hot,..." or from context "When the water is hot,...")

This pattern works well with participles:

When running, try to drink water.

If tired, take a break.

But these are all intentionally shorter than would be "natural" in regular conversation.

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