The key word in the following recommended frequencies based on the number of times any of the words in your keyword on the page, divided by the number of words in the sentence. The recommendations listed, updating information on Google from April, May 2008 and at any time. Other search engines May require or propose different frequencies, but the figures are below what one has proposed to follow.

TITLE MOT FREQUENCY: A keyword frequency of 1 for the title.
Title Area of words: A word from 5 to 7 is proposed for the title.
The text of the link between importance KEYWORD: A keyword space of at least 58% for the text of the links.
Web MOT FREQUENCY: a keyword frequency range from 1 to 16 is proposed for the URL link.
Text MOT FREQUENCY: A key word frequencies from 2 to 15 is proposed to the body of the text.

Google now uses technology from the word, is a process in which Google and other search engines, the search for key words, and any change in the key word. One possibility for which this is your keyword, both singular and plural versions in Google. If the results are equivalent, then use Word Tracker to decide which version has more potential for traffic with the smallest number of competitors.