A keyword is a word or phrase tied to a search. In SEO it's a data description of how people phrase a need. You don't have to repeat it in every sentence.
What a keyword really is
Every query has an intent behind it. "seo consultant cost" probably calls for pricing and terms of cooperation, while "what does an seo consultant do" needs an explanation of the role.
One page can gain visibility for many related phrasings. Meaning and overlap in the results decide whether they belong together. A fixed number of keywords per URL doesn't.
Intent matters more than volume
Search volume shows the size of the demand. It says nothing about its value. Judge a query together with intent, competition, the shape of the SERP, how well your offer fits and the chance of earning a useful click.
A smaller, specific query can be worth more commercially than a generic term. That doesn't mean every long-tail query automatically converts better or faces weaker competition.
Where people go wrong
- picking keywords by search volume alone,
- creating a new URL for every synonym,
- ignoring existing pages and cannibalization,
- using internal jargon instead of the customers' words,
- repeating a phrase at the expense of readability.
Good research connects queries to specific URLs, content, a business goal and a plan for regular updates.