A semantic component is a combination of words, also known as a "composite of lexical units" that attends to the meaning of such word combination and is interchangeable as long as it retains the same meaning. In not so many words, a semantic component is the part of a word that deals with its meaning, and not with its morphology (word form), or syntax (word placement).
Therefore a semantic component, when it is interchangeable it is known as a "common" semantic component, or a "shared" semantic component. For instance the words humanity and mankind are interchangeable and refer to the same thing because they share the same semantic component.
When they are not interchangeable, it is used to contrast two separate words with similar meanings. For example, when you refer to something as "neutral", you are automatically placing weight in its meaning and differentiating it from words such as "partial, impartial, or agreeable and disagreeable".
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