Irreversible inhibitors are molecules that bind onto active sites of enzymes and inhibit that enzymes functionality, inhibit their activity. Now, the thing about these Irreversible inhibitors is they can bind onto the active side either by covalent or noncovalent means. But once they bind onto that active side, they will not let go. And that means they bind very, very, very tightly, very, very strongly. And even if we remove access inhibitor from that mixture, that will not dissociate that inhibitor, that will not reform that active version of the enzyme. So, all the different types of inhibitors, irreversible inhibitors that we have in nature and that we can synthesize in a lab, can basically be categorized into three different groups, into three different categories.