How to make a random value harder to be selected?

Background

So in my game I'm making a function where it selects values in a table:

function chooseRandom(randomEntry)
	return randomEntry[math.random(#randomEntry)]
end

Question This chooses values randomly in the table; however, how would I go about making a certain value harder? The values in my tables are strings such as:

local Flames = {
	"Sky","Sun","Storm","Rain","Mist","Lightning","Cloud","Night","Earth",
}

Is the only the possible way to do is by adding more of the other values and making it more scarce?