Check out example codes for "bs4 no border". It will help you in understanding the concepts better.

Code Example 1

<!-- Subtractive -->

<!-- Removes all borders -->
<span class="border-0"></span>

<!-- Removes border at given direction -->
<span class="border-top-0"></span>
<span class="border-right-0"></span>
<span class="border-bottom-0"></span>
<span class="border-left-0"></span>

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