Emotions Need to Be Understood...How?

When someone says "I feel sad" how do we know, exactly, what that means to the individual? Likewise, when someone says "I love you", what does that mean? Does it mean "friendship love", surface good feelings or deep, intrinsic feelings of spiritual love. In other words, there are such extreme RANGE OF EMOTIONS that it is difficult to conceive of the exact understanding of that word "Love" (or other words and there meaning" unless we have a basic skill set for understanding emotion as it relates to the collective human animosa.