The words “rational” and “rationale” are very easy to mix up. After all, they sound similar and look similar written down. In addition, these words are not hugely common, so you may not be familiar with how they are used. But there is a difference! Let us explain.
Rational (Logical or Reasonable)
The adjective “rational” typically means “logical” or “reasonable.” We would use it like this:
I did research so I could make a rational choice about where to study.
It can also mean “capable of exercising reason,” such as in the following:
A rational thinker will always seek other opinions before making a decision.
In both of these cases, “rational” is related to the idea of acting based on reason rather than emotion. The adverbial form of this word is “rationally,” and the opposite of “rational” is “irrational.”
“Rational” also has a very specific meaning in mathematics, where it refers to a number that can be written as a fraction. However, you will only need to know this if you’re studying math!
Rationale (A Reason for Doing Something)
A “rationale” is a reason for doing something. It would be used in a sentence like this:
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The policy was based on an economic rationale.
Here, for instance, the term “economic rationale” refers to using economic factors to explain an action. You might also be asked to write a research rationale for an academic paper.
Importantly, this term is a noun (i.e., a naming word). This makes it very distinct from “rational.”
Rational or Rationale?
To avoid errors in your writing, remember that “rational” is an adjective and “rationale” is a noun. Thus, if you need a descriptive term, it will be “rational.” If you need a noun, on the other hand, it will be “rationale.”
Rational (adjective) = Reasonable or based on clear thinking
Rationale (noun) = A reason for doing something