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Key words connected by Boolean operators will be matched regardless of how far apart they are in a document. But you may want to retrieve documents only if the keywords are close together. For example, the word 'train' (meaning railway engine) might be expected to occur close to 'railway', 'electric' or 'diesel'.
You can use proximity operators to specify the positional relationship of key words.
One such operator is 'w' (within), followed by a forward slash and number. This operator is used to specify the number of words within which the key words must be found in relation to each other. For example, 'murder w/10 provocation' means the words must be within 10 words of each other (in either direction).
If you want to insist that one key word must occur before the other, the operator 'pre' (preceding) followed by a forward slash and number, gives the required 'ordered' proximity. An example is: 'provocation pre/10 murder'.
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