What is the difference between القاضي and قاض ?Feel free to just provide example sentences.

قاضي
Is اسم منقوص
So if it's indefinite, you have to delete the yaa'.. قاض

الاسم المنقوص is a noun ends in the long vowel ي, with a short vowel (kasra ـِ ) below the letter before last

E.g
قاضِي, داعِي, ماضِي, جارِي..

If the noun is indefinite, then you need to drop the ي letter

If it's definite , then you don't need to
Like if it's connected with the definite article
القاضي

Or if it's definite by the addition معرفة بالإضافة
( definiting the indefinite by adding something definite

Like
قاضي المحكمة
the court judge.

ماضينا
Our past

محامي اخي
My brother's Lawyer

So, like we want a new lawyer
نريد محامٍ جديد
Nureedu mu7aamen jadeed
Not محامي