A family of Microsoft word processing software products for creating web, email, and print documents.
The "fix" is to clear the option "When selecting, automatically select entire word" as mentioned earlier in this thread by NateMenz. I do that routinely, and I don't miss the so-called "convenience". If I want to select a whole word, I just double-click it.
If you uncheck the option and Word still selects a whole word when you single-click inside it, it's being interpreted as a double-click. That can happen when your mouse malfunctions and the switch under the mouse button "bounces". The part about selecting a whole paragraph when you click twice is additional evidence -- Word should need a triple click to select a paragraph. In that case, try using a different mouse.