Your keyword must be relevant to the title and page contents. Don’t use keywords that are not relevant or not matching the contents of your pages, even if it is highly searching one. Use only keywords that best suite to your contents.
Number of keywords
Next factor we have to consider is the number of keywords appearing on a single page. It is advisable to keep the keyword intensity to three to four for a particular keyword. If you use the same keyword more than four times, the search engine finds that you are spamming or artificially add keywords, and some search engine penalizes for it.
This is also an important factor. If you use a keyword four times on a page containing 100 words, the keyword density is 4%. It is advisable to keep keyword density between 4-7%.