Question

How to make a better related questions by avoiding common words?

Answer 1

This is actually already working in your site. Maybe you just have to tweak it to your needs.

Just open the qa-config.php file and you'll see this. I think it is self-explanatory :)

If a word is used QA_IGNORED_WORDS_FREQ times or more in a particular way, it is ignored when searching or finding related questions. This saves time by ignoring words which are so common that they are probably not worth matching on.

define('QA_IGNORED_WORDS_FREQ', 10000);

The only thing that is worth mentioning is that in a particular way refers to words in title, words in content and words in tags. They are tracked separately.

Comments

Some keywords in a general category site will be more than in numbers than those common words. So an option of ignoring some preconfigured common words is always good.

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"will be more than in numbers than those common words" => I don't quite get that. If the words are common, then they are ignored by the "Ignore common words" feature. Wouldn't it be redundant for you to specify common words manually that happen to already be common?

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In a q&a site, all those titles are in question form. So the most common words will be words like ' What when how can do does to I you ' etc. But in some cases, some keywords will be more common than these words. That's why I am asking for a manual way to specify those common words.

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"But in some cases, some keywords will be more common than these words." => So if a word like "What" has 12449 references and you have a cooking site you're saying that the word "Spoon" might appear 16338 times. It makes sense.

Now, both words exceed the 10000 limit I mentioned in the answer. So they are both automatically ignored. Manually ignoring "Spoon" makes no sense and is redundant. It will only slow the searches unnecessarily. If you still consider this is relevant for you, you can always write a plugin to take care of it