When a concordance is made of a certain word, that word is the key word, and in a concordance it appears in context, i.e. with a predefined number of words to the left and right. It is the 'key word'. This term is used in measuring the length of a text. Each successive word-form is counted once, whether or not that particular form has occurred before. This is the measurement, in words, of the co-text of the node.
Text file Almost all concordancers require corpora to be saved as a text file.
This is the simplest form of file on which words are stored. There is no formatting. A text file can be read by any computer regardless of operating system. In the windows environment, the name given to any text file must end in '.txt'. The 'tokens' of a corpus refers to the simple word count, the number of running words in the corpus.