Word for a sentence structured like: 'Something is to something as something is to something'

No matter how they're written, they're called analogies:

An analogy is a statement that suggests two terms are related to each other in the same way that two other terms are related to each other. The [Miller Analogies Test] analogy items are written as equations in the form “A : B :: C : D.” This can be read as either “A is related to B in the same way that C is related to D” or as “A is related to C in the same way as B is related to D.”
_{The Miller Analogies Test Study Guide}

What Were SAT Analogy Questions?

These were the original stereotypical SAT questions. You were given a pair of words and asked to choose from five other pairs of words to find the relationship that most closely resembled that of the first pair.

In the following example, you can interpret the dots as the words “is to” so you would think of it as “Paltry is to significance as _______ is to _________.” where the blanks are the two words in one of the answer choices.

PALTRY : SIGNIFICANCE ::

A. redundant : discussion
B. austere : landscape
C. opulent : wealth
D. oblique : familiarity
E. banal : originality

(the correct answer is E)

_{SAT Analogies and Comparisons: Why Were They Removed, and What Replaced Them?}

This weekend, co-vocabularists are invited to submit novel analogies, using the tried and trusted formula: A is to B as C is to D.
_{Weekend Competition — NYT Opinion Pages: Schott's Vocab}