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.
There are many ways to write. You can do so meticulously with elegant, precise penmanship, or you can scrawl—which is pretty much the opposite. The verb scrawl is defined as “to write awkwardly, carelessly, or illegibly.” If you hastily scrawl your name across a blackboard, you are writing it in a sprawling, awkward manner. The origin of this word is uncertain, but it may have been influenced by an earlier use of scrawl to mean “to scramble or crawl.” The hurried disorderliness inherent in scramble, which shares the first three letters with scrawl, is indeed what sets scrawl apart from other more measured synonyms for write, such as draft, compose, and pen.