What does grow'st from Shakespeare's sonnet 18 mean in modern English?

Answer 1

Shakespeare actually wrote in modern English, and the verb form you are asking about is, though now very rare, still in occasional use. Basically the story is this: if you see a familiar word with "-st" on the end, you will probably find the pronoun "thou" lurking close by. "Thou" always takes verbs ending in -st; "thou thinkest" is the same as "you (singular) think". Shakespeare used them interchangeably. Note this passage from King Lear:

Have more than thou showest,

Speak less than thou knowest,

Lend less than thou owest,

Ride more than thou goest,

Equals show, know, owe, and go. "Growest" obviously is "grow"

Answer 2

It means something like "Beauty is transitory; poetry lasts longer." If that sounds a bit flat, it is. Asking for what a poem is all about without the words the poem is written in is like asking what The Mona Lisa would look like if it were drawn with three crayons, what a Beethoven symphony would sound like on a plastic recorder, or a great Electric Guitar solo would sound like if it were played on a cigar box and a couple of rubber bands.

In other words, do not cheapen the art to suit you, make yourself greater by aspiring to comprehend the greatness of the art the way it was created.

Answer 3

"Grow'st" in this context means "growest," which is an archaic form of the modern English word "grow." In modern English, this phrase from Shakespeare's Sonnet 18 would be translated to "you grow."