Mentality is a particular way of thinking that a person or a group carries around — a habit of mind, especially one you think is wrong or foolish. We say a siege mentality (the feeling that everyone is against you), a victim mentality, “that old mentality.” When you say “that mentality,” you are often not praising it. Neutral uses exist (“the mentality of engineers who want a clean design”), but the word easily leans toward “this is how they are, and it is a problem.” It is built from mental + -ity. French mentalité is a close twin. These days many people prefer mindset when they want a kinder or more fashionable word. Mentality is still common, a bit more formal or critical. Though actually, it does not mean “how clever you are.” That is intelligence, not mentality. And it is not the slang use of mental for “crazy,” which is unkind and not this noun. Mentality is the shape of the thinking, not the horsepower, and not a word for mental illness. You can talk as if a mentality can shift; that may be hopeful, but it is how the word is used.