Check out example codes for "css font size". It will help you in understanding the concepts better.

Code Example 1

.class {
	font-size: 12px;
}

Code Example 2

<span style="font-size:20px;"></span>

Code Example 3

#selector{
    font-size:20px;
}

Code Example 4

p {
	font-size: 150% /*px, cm, in, etc.*/; 
}

Code Example 5

font-size: 2em;

Code Example 6

// to scale font size in relation to its parent element
style="font-size: 2vw;"

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