According to Longman Dictionary of Contemporary English: Use first, first of all, or firstly to introduce the first item in a list of two or more points, instructions etc • First, make sure the screws are securely fixed in position. Then attach the wire. According to American Heritage: It is well established that either first or firstly can be used to begin an enumeration: Our objectives are, first (or firstly), to recover from last year's slump.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.