firstly

1. ADV You use firstly in speech or writing when you want to give a reason, make a point, or mention an item that will be followed by others connected with it. 第一 (演講、文章中用于列舉條目); 首先[ADV with cl/group]

The programme is now seven years behind schedule as a result, firstly of increased costs, then of technical problems. 該計劃現在比預定的計劃晚了7年，首先是因為費用增加，其次是由于技術問題。