What is another word for smaller?

There are many words you could use depending on the context. Here are some options:

General:

* Lesser

* Miniature

* Tiny

* Diminutive

* Little

* Slight

* Compact

* Petite

* Short (for height)

* Narrow (for width)

* Thin (for thickness)

More specific:

* Shorter (for length)

* Narrower (for width)

* Thinner (for thickness)

* Lighter (for weight)

* Fewer (for quantity)

* Less (for amount)

* More compact

* More petite

Informal:

* Smallish

* Little bitty

* Wee

The best word to use depends on the specific situation and the intended meaning.