Something that is tangible is able to be touched and thus is considered real.
A contagion is a disease—or the transmission of that disease—that is easily spread from one person to another through touch or the air.
Something that is integral to something else is an essential or necessary part of it.
A tangential point in an argument merely touches upon something that is not really relevant to the conversation at hand; rather, it is a minor or unimportant point.
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