It's about 15 or 20 words we should memorize that show up a lot to introduce conditional logic, and we want to memorize for each word whether it introduces a sufficient condition that we would put on the left side of the arrow, whether it introduces a necessary condition that we would put on the right side of the arrow, or whether it's one of those special, if not words like unless, that we saw in the previous problem. The most common sufficient triggers are things like if, when, where, whenever, wherever, any universal, like all each, any, every. And the only is a sneaky little counter example, because only an only if, and only when, are the most common necessary trigger words. You'll also see words that sound like a guarantee, things that ensure imply guarantee, always lead to something else, introduce a right side idea. And words that introduce necessity, if we're saying that we require something, we need it, we depend on it, that thing also would go on the right side on the necessary side. In fact, it's just really nice to remember that if it's required, it goes on the right.