How to number the definitions and theorems separately?

This is the syntax that I have written but in this syntax definitions, theorem, note, remark are numbered continuously like definition 1, theorem 2, theorem 3, note 4 and so on. But I need to number the definitions theorems separately like definition 1, definition 2, theorem 1, theorem 2 and so on. What should I change in the following syntax to number them separately.

documentclass[a4paper,12 pt]{article}
usepackage{amsmath,amsthm,amsfonts,mathrsfs,amssymb}
usepackage{amssymb,latexsym,pstricks,pst-grad}
usepackage{enumerate}
usepackage{array}
usepackage{fontenc}
usepackage{multirow}
usepackage{longtable}
usepackage{pdflscape}
usepackage[english]{babel}
usepackage{booktabs}
usepackage{multicol}
usepackage{tabularx}
usepackage{colortbl}
usepackage{array, makecell}
usepackage{siunitx}
usepackage{caption}
usepackage{float}
usepackage{graphicx}
usepackage{mathtools}
%usepackage[
%top    = 2.75cm,
%bottom = 2.50cm,
%left   = 3.00cm,
%right  = 2.50cm]{geometry}
%usepackage[margin=in]{geometry}
usepackage[nottoc]{tocbibind}
newtheorem{thm}{Theorem}[]
newtheorem{illustration}[thm]{Illustration}
newtheorem{cor}[thm]{Corollary}
newtheorem{lem}[thm]{Lemma}
newtheorem{pp}[thm]{Proposition}
newtheorem{ppty}[thm]{Property}
newtheorem{defn}[thm]{Definition}
newtheorem{rk}[thm]{Remark}
newtheorem{ex}[thm]{Example}
newtheorem{result}[thm]{Result}
newtheorem{note}[thm]{Note}
newtheorem{obs}[thm]{Observation}
newtheorem{case}[thm]{case}
newtheorem{subcase}[thm]{subcase}
newtheorem{Prop}[thm]{Proposotion}
newtheorem{property}[thm]{property}
renewcommandthesection{arabic{section}}
newcommand{NI}{noindent}