What words are repeated in William Shakespeare's "Sonnet 12" and why?

The one word that is repeated in this excellent example of
a Shakespearian sonnet is the word "time." Throughout the sonnets, and especially
towards the beginning, Shakespeare attempts to describe the idealised beauty of the male
object of the sonnets, though always referring to the fact that such beauty will wither
and fade with the passing of time. Time is such a key theme of all of his sonnets that
he either tries to immortalise his beloved's beauty in his verse or, as in this sonnet,
advises his beloved to have children so as to perpetuate his beauty. Let us examine the
use of the word time in this poem and see how it fits in with the overall
purpose.

The first two lines of this sonnet present "time"
as a negative thing, something that robs beauty and withers and
decays:

When I
do count the clock that tells the time,

And see the brave
day sunk in hideous night;

It
is "time" that transforms the "brave day" into "hideous night" and likewise is
responsible for the passing of the seasons, which fills the world with signs of the
death of nature. It is contemplating the havoc that time wreaks in nature that forces
the speaker of the poem to realise that time, which is responsible for the decay and
withering that he sees all around him, will have a similar effect on his
beloved:

Then
of thy beauty do I question make, 
That thou among the wastes of time must
go,
Since sweets and beauties do themselves forsake
And die as fast
as they see others
grow;

However beautiful the
beloved is now, he, like everyone else, is destined to go "among the wastes of time."
Note the negative way that time is presented here, linked to the word "wastes." Thus
Shakespeare reinforces the effect of time on the human
body.

Lastly, "Time" is personified as a Death-like figure,
with a scythe, who is presented as all powerful and whom cannot be cheated, except by
having children which would allow the beloved to create a temporary defence against the
ravages of Time:

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And nothing 'gainst Time's scythe can make
defence
Save breed, to brave him when he takes thee
hence.

Thus it is the word
"time" that is repeated in this sonnet, which of course emphasises the central theme of
the poem, which focuses on the ephemeral and fading beauty of the beloved and the impact
of time upon us all.