Microsoft Word has an annoying feature where it's always selecting the entire word even when you are just trying to select a portion of a word. To get better control over what is being selected, you can turn this "feature" off in MS Word. Go to Tools > Options (or Word > Preferences... if you are on a Mac) and then select the Edit tab. There will be an option called When selecting, automatically select entire word, uncheck the box next to it and you'll be able to select portions of words much more easily.