Longman Dictionary of Contemporary English - firstly

~ adv sentence adverb used to say that the fact or reason that you are going to mention is the first one and will be followed by others  (Firstly, I would like to thank everyone who has contributed to this success.)  ( USAGE NOTE: FIRSTLY WORD CHOICE firstly, first (of all), in the first place, to start/begin with, at first, in the beginning Firstly/first (of all)/in the first place/to start with/to begin with are often used to introduce a series of reasons, ideas, remarks etc There are three reasons why I don't like him first (ly)/to start with he's rude, second (ly) he's a liar, and third (ly)/finally he owes me money. You use first (of all) (NOT firstly) to introduce a series of actions, often in order of time First of all I get dressed, next I bring in the paper, then I fix breakfast. At first can only be used for a period of time, often when you are comparing it with a later period. To start/begin with and in the beginning can be used in this way too You'll find it difficult at first/to begin with, but later/soon it'll get easier. )