I am trying to implement a recurrent neural network machine translation system, and I am just learning the things.I am creating a word embedding matrix. In order to do that, I should know my vocabulary size, dimension of the embedding space, and context window size?What is context window?
What is context window size?
rnn;machine translation
A context window applies to the number of words you will use to determine the context of each word. Like of your statement is the quick brown fox  a context window of two would mean your samples are like (the,quick) and ( the, brown). Then you slide one word and your samples become  (quick, the ), (quick, brown) and (quick fox) and so on. I would suggest reading up this word 2vec tutorial to understand the training method and terminology. 