Every single word has at least two meanings. There are the obvious meanings listed in the dictionary we all become familiar with. These are the definitions of the words. For example, we define the word 'home' as 'a place of residence' but it is also 'to move or be aimed toward,' like a homing pigeon. One word, two definitions.
However, there are more to words than definitions. In his book 'Everything is Illuminated,' Jonathan Safran Foer weaves an intriguing, and sad, tale from two disparate parts. One of them is that of a Ukrainian named Alex, writing a story about his adventure with the author. In his broken English he writes such titles as 'An Overture to the Commencement of a Very Rigid Journey.' His sentences unfold likewise: '[He] is always promenading into things. It was only four days previous that he made his eye blue from a mismanagement with a brick wall.'
What he says is accurate to the definition of the words; one of the definitions of 'rigid' is 'hard,' and 'to promenade' is 'to walk.' What he says is accurate, but how he says it indicates he's not a native speaker. His use of words falls strictly into the structural definitions they carry; his grasp of the language falls below the mark that gives one the ability to speak naturally and effectively.
Another example seems in order. I'm getting pretty heavy on the linguistic jargon.
When you are in a relationship with someone, and i'm talking about more than friendship, you can rightfully say you belong to them, you are theirs, they are yours. It's entirely appropriate to use possessive pronouns when talking about them: my girlfriend, my husband, my lover. However, were you to use 'possess' or 'own' instead of 'belong,' the meaning changes drastically, despite their shared definitions.
When i am owned by you, i become a slave. It's a useful word for property, but people are not property.
When i am possessed by you, my body is not in my control. Demons possess you, people do not.
Each word--possess, own, belong--shares at least one definition with the other two; this does not make them at all interchangeable. If A equals B, and B equals C, that does not mean A always equals C, at least not with language.
Every single word has at least two meanings: one is the definition listed in the dictionary and the other is what meaning we place behind it. This connotation of words drives our language. Without it, we lose nuance and subtlety. With it, we hold multiple meanings with a single word.