"Ti"

Ti → little, small.

"Ti" is used as an adjective.  Always placed before a noun.

A little boy.

yon ti gason.

A little house.

Yon ti kay.

I found a little book.

Mwen jwenn yon ti liv.

Wait a little while.

Tann yon ti moman.

A small car is better than a big car.

Yon ti machin pi bon pase yon gwo machin.

Piti is also Haitian Creole for small, little.

"Piti" is an adjective.  It is never placed before a noun.  It may be used as an adjective or adverb.

This house is small.

Kay sa piti.

This dress is too small for you.

Rad sa twò piti pou ou.

Why is this car so small?

Poukisa machin sa piti konsa?

I'm small, but I'm strong.

Mwen piti, men mwen fò.

"Pitit" with a "t" at the end means  child, offspring.  You may use it to describe a small or grown child.

How many children do you have?

Konbyen pitit ou genyen?

All my children are in college.

Tout pitit mwen nan kolèj.

Is this your child?

Eske sa se pitit ou?

And finally, another to say "child" in Haitian Creole is "timoun".