Definition of Synesis
Synesis is a traditional grammatical term derived from a Greek phrase meaning unification, sense, meeting, or realization. It is a rhetorical device in which the conventional grammatical settlement of syntax is replaced by using an agreement in its sense. In other words, synesis is a grammatical production this is in agreement with the sense instead of the strict syntax. It is used to focus on the words’ creation consistent with the sense no longer its morphosyntactic form. Such as:

“Fat, drunk, and silly is no manner to go through life, son.”

(Animal House through Harold Ramis, Douglas Kenney, and Chris Miller)

Types of Synesis
Kinesthetic imagery is similarly divided into two categories:

Notional harmony or notional settlement is one sort of grammatical settlement in which the agreement is made with the that means of a noun in place of complying with a strict syntactic requirement.
Situational agreement involves the singular and the plural forms of a phrase being the same. Its singularity or plurality depends upon the interpretation or intentional emphasis of the author or speaker.
Difference Between Synesis and Anacoluthon
Synesis is a form of anacoluthon, which is a syntactic interruption. Though each are anti-grammatical constructions but are different. It is because synesis is used to focus on the phrase creation in line with their sense in preference to grammatical shape. For example:

“Among the growing numbers of men looking for his services, a extensive proportion are spurred to accomplish that by means of lady voices…”

(Europe’s Extraordinary Makeover, by means of Catherine Mayer)

On the opposite hand, anacoluthon is the disruption within the grammatical float of the phrases, by way of beginning another sentence immediately. Such as:

“A plank that changed into dry was not worrying the odor of burning and altogether there has been the fine kind of sitting there could by no means be all the edging that the most important chair was having….”

(A Portrait of Mabel Dodge, by means of Gertrude Stein)

Examples of Synesis in Literature
Example #1: The Adventures of Huckleberry Finn (By Mark Twain)
“What’s the use you gaining knowledge of to do proper, while it’s troublesome to do right and it ain’t no hassle to do wrong, and the wages is simply the same?”

In those lines, the writer makes use of the plural form of “wage,” with the auxiliary verb “is,” that's syntactically wrong. However, the settlement of the phrases is made according with the sense, which is to say it's far singular in a sense, but plural in form.

Example #2: 1984 (By George Orwell)
“For, after all, how will we know that two and make four? Or that the force of gravity works? Or that the beyond is unchangeable? If each the past and the external global exist best inside the thoughts, and if the thoughts itself is controllable – what then?”

In this excerpt, the grammatical construction of the words “ and two make four,” which ought to be “makes” in place of “make.” The arrangement isn't always made in morphosyntactic form. Instead, the phrases are arranged in keeping with their logic.

Example #3: Wagner’s Parsifal (By Charles D. Warner)
“Most of the audience had been standing, and the house turned into in a buzz of verbal exchange and expectation.”

Here, the word “audience” takes the range with the word “become” because with this auxiliary verb, it frequently concurs grammatically. However, it's miles in harmony with “have been,” that is correct logically and not grammatically.

Example #4: King Lear (By William Shakespeare)
“I will have such revenges on you both,
That all the global shall–I will do such things,
What they are, but I recognise now not…”

In this passage, Shakespeare makes use of “revenges” inside the sentence, that is plural in sense. It is logically true, but syntactically wrong.

Function of Synesis
Synesis is commonly used in writing as a planned effect. Often it is employed in dramatic monologues, prose, and poetry. Synesis is often used in the circulation of consciousness style of writing, since it is a basic function of casual thoughts. Apart from that, the most vital characteristic of synesis is to draw the eye of readers by way of permitting them to prevent and recall the underlying which means. Usually, it causes confusion in the minds of readers, and makes them comprehend the motive of construction of words in keeping with their logic, instead of grammatical form. Synesis is widely used in media and political public speeches.
Synecdoche Synesthesia