Analysing Sonnet 126 O thou, my lovely boy, who in thy power

O thou, my lovely boy, who in thy power

Dost hold Time's fickle glass, his sickle, hour;

Who hast by waning grown, and therein show'st

Thy lovers withering as thy sweet self grow'st;

If Nature, sovereign mistress over wrack,

As thou goest onwards, still will pluck thee back,

She keeps thee to this purpose, that her skill

May time disgrace and wretched minutes kill.

Yet fear her, O thou minion of her pleasure!

She may detain, but not still keep, her treasure:

Her audit, though delay'd, answer'd must be,

And her quietus is to render thee.

Famous Shakespearean sonnet, or short poem, entitled William Shakespeare Sonnet 126 O thou, my lovely boy, who in thy power.
In this sonnet,the words in bold and underlined aren't used anymore, they are called archaic. These words changed, below are the actual forms.

In Northern English and Scots English, thou is still used as the second person singular pronoun.

Thou is the nominative, while the objective form is thee and the possessive is thy or thine.

The verbs that follow thou normally end in -st or est, as you can see in this sonnet.

Thou having been replaced by the pronoun You.

Thy having been replaced by the possessive adjective Your.

Dost having been used as the 2nd person singular present indicative of Do.

Hast having been  used as the 2nd person singular present indicative of Have.

Mistress having been used as an archaic or dialect title equivalent to Mrs.

Mistress having been used as an archaic or dialect word for Sweetheart.

Pluck having been used as the verb to pull(something) forcibly or violently(from something or someone).

Thee having been replaced by the pronoun You and reflexive pronoun Yourself.
Audit having been used as an audience.