One prefix for smaller is micro- For example: microwave, microburst
The prefix "de-" means to reverse the action or make something less or smaller. For example, "deflate" means to make something smaller by removing air.
to make something less or smaller using
Something you can make smaller is a bouncy ball because, you can take air out of the bouncy ball.
To make smaller or use less of something
The prefix "re-" means to do something again or to go back to a previous state. It does not typically signify making something less or small.
It appears there may be a typo in your question. If you meant to ask about "reduce," it means to make something smaller in size, amount, or degree. It can also refer to simplifying something or making it more manageable.
To make smaller or less to cause to appear so.
"Diminish" means "to make or become smaller: to make something smaller or less important, or to become smaller or less important." Used in a sentence: If you must pay monthly bills and do not have a job, your savings will quickly diminish.
The main threat in a tornado is flying and falling debris. If you make yourself a smaller target you are less likely to be hit by something.
An SI prefix, unless that unit already has a prefix.
A prefix comes before the word, and suffix comes after it. A prefix is something like "un-" as in undone, unnecessary, or unheeded. A suffix is something like "-less" as in helpless, useless, or timeless.
You could add the prefix in- to it to make the word inexpert.