A 'decree nisi' is the first of two 'orders' which you need to obtain to finally end your marriage. The second order is called a 'decree absolute'. You will be able to apply for a decree nisi after you have sent your divorce petition to court and your spouse has indicated that he/she does not intend to defend (argue against) the divorce.
To apply for a decree nisi, you will need to complete an 'Application for a decree nisi (Form D84)', together with an 'Statement in support of divorce' confirming the reasons why you want a divorce.
There are five different statements in support of divorce and you will need to complete the one relating to the reason for your divorce. The statements are as follows:
If the court is satisfied that there are grounds for divorce, it will send you and your spouse a 'Certificate of entitlement to a decree', which will tell you the date and time when the judge will grant your decree nisi. However, you do not have to attend court in person for this.