Vocabulary in Sonnet 18

“Eternal lines” takes on multiple interconnected meanings. The “lines” can refer to lines of poetry, referring to the speaker’s desire to preserve the fair youth through verse. The “lines” can also refer to genetic lineage, another means by which the fair youth can preserve his own image through time. Shakespeare seems to be equating these two lines, artistic and genetic. In the preceding poems, the speaker urged the youth to procreate; now the speaker weighs the benefits of poetry as a means of passing on the youth’s essence.

In the poem’s third use of “fair,” we encounter a third meaning of the word. “Fair” now takes on the noun form, serving as a shortened version of “fairness.” The shifting use of the word is indicative of Shakespeare’s linguistic play. In a deeper sense, the changing definition of the word “fair” represents “nature’s changing course”—the passage of time that decays all fair things.

Shakespeare uses “fair” in two senses. The first “fair” means “one who is fair,” or beautiful. In its second instance, “fair” is used in its typical form as an adjective. The line tells of the inevitable fading of physical beauty: on the surface, fair people will lose their fairness.

“Temperate” has a dual meaning here. It means both having a calm and even temperament, and “a period of time.” This description of the youth embodies not only his perfect character, but the ability of this perfection to outlast time. He is unconfined by the changing of the seasons.