If + adjective or adjective phrase

Question

I notice lots of sentences use if directly followed by an adjective or an adjective phrase, for example:

If necessary, please import more of these types of goods.

If a little taller, he could reach to the book on the bookshelf.

This appears to be one of the places where English lets you omit words and consider them to be "understood". However, all grammars about if I googled are talking about conditional clauses; none is talking about if + phrase.

Can anyone explain the general rules of if + adjective or adjective phrases?

Answer 1

It's another instance of elliptical structure. It's not that the if-clauses you demonstrated in your example sentences are not conditional. They are, but some words are left out - elliptical structure.

Sometimes we can leave out subject + verb after the conjunction if. When it's expanded it forms the familiar conditional clause structure.

If in doubt, ask for help. [ = If you are in doubt, ask for help. (Here if-clause is also a conditional clause)]

If necessary, please import more of these types of goods. [ = If it's necessary, please import more of these type of goods.]

If a little taller, he could reach to the book on the bookshelf. [ = If he was a little taller, he could reach to the book on the bookshelf.]