Begin or begin by?
I don't know how to say in English 'Voy a empezar definiendo....(algo)". I have 3 options: 1) I'll start by defining something 2)I'll start defining something 3) I'll start with a definition
Which one is correct (if any)?
I added the third one because I the one I feel is correct but is not the one that make me happiest.
Thank you,
Leandro.
4 Answers
They are all correct, but mean slightly different things:
"I'll start by defining" or "I'll start with a definition" both mean tht the first (ie. next) thing you are going to do is define something.
"I'll start defining something" means you are going to start to define something.
The difference in meaning is pretty small.
The first one is probably what you want to say, depending on context. Math and science teachers use that phrase a lot.
All of your suggestions are perfectly good. There is no great difference among them. Each one will be easily understood and no one will think twice about what you mean. (I have just given you a much more elaborate example of three ways -all good- of saying essentially the same thing.) Be confident. You are off to a good start.
The word "by" implies that this is the first of many things you are going to do. For example, If I said "I am going to begin by observing", a person would probably think that you are going to observe, then take notes, then write a paper or something of the sort. Without the "by" you are simply doing this thing, there is no assumption that it is the first of a list of things. As to which is correct, I'd say the second one, but I'm not sure.
The best English translation would probably be "I'm going to begin defining something".
When you use 'by', it almost means (maybe just a connotation difference) 'by means of'
How could you ever explain that to me? - I'll start by (means of) defining something
Please correct me if I'm wrong 
