If your grocery list includes cheese and bread, it means that your (very sandwich-friendly) grocery list contains these items, likely among other items. Your list might also include pasta, lettuce, and orange juice. The synonym encompass means “to include comprehensively.” Paying special attention to that last part, “comprehensively,” let’s revisit the aforementioned grocery list: it would not make sense to say that your grocery list encompasses cheese and bread; rather, you might say that your list encompasses a wide range of primo ingredients for a full three-course meal. The use of this verb broadens the scope of your list, and suggests that you’ve included a generous sampling of ingredients to satisfy all your hungry guests, from aperitif to dessert.

The noun reason is used a few different ways. Sometimes it refers to a justification, as in, I dare you to give me one good reason for quitting school! Other times it refers to a cause or basis for some belief, action, fact, or event: The legislator said the reason for the new bill was to reinvigorate the local economy. The synonym rationale is closer to the latter, but it implies a more detailed exposition of thought or logic. When someone asks for a rationale, chances are that they aren’t expecting an excuse or justification. More likely, they hope to understand the thought process or the fundamental reasons that serve to account for something.

The adjectives equivalent and tantamount imply a correspondence between two or more things. Equivalent is the more general term, and it has a wider application. You might encounter it used in the context of quantities or measurements; in a recipe, for instance, if you substitute one ingredient for another, you might use an equivalent amount of the substitute. Tantamount is a far less common word, and it is used to talk about immaterial things that are equivalent in value, force, effect, or signification. The correspondence implied by tantamount is a little looser and open to interpretation—and this descriptor is almost always used with the preposition to, as in, His angry speech was tantamount to a declaration of war.