Rationality

We get so used to the English language that it becomes easy to overlook the many oddities and exceptions that a non-native speaker would find baffling.  I used not to care much about such things, but over time my attention to the nuances and mysteries of language has become second nature.  Of course, we have all competently used the rules of grammar, but we do so mostly out of habit.  Case in point, think about the phrase “used to”.  What does the word “used” mean?  How does that meaning fit into the phrase “used to”?  Look at how the words are used in the first three sentences of this paragraph – does it mean the same thing in each case?  Isn’t it weird?