Why is blank verse used in A Midsummer Night's Dream?

Blank verse is used to set apart the noble or higher class characters in the play, such as Theseus or Hippolyta. Blank verse indicates that they speak using a superior, upper-class diction.

Blank verse is unrhymed iambic pentameter. Iambic pentameter means there are five unstressed and five stressed syllables in a line, with the second syllable stressed. This is the pattern: ta-DA, ta-Da, ta-Da, ta-Da, ta-Da. We hear this, for example, when Theseus talks about his wedding day. Each line below is in iambic pentameter:

Now, fair Hippolyta, our nuptial hour
Draws on apace. Four happy days bring in
Another moon. But oh, methinks how slow ...

The fairies, in contrast, speak in trochaic verse, in which the stressed syllables are the opposite of iambic verse. They speak with four stressed and four unstressed syllables per line: TA-da, TA-da, etc. This sets them apart as supernatural beings.

It is interesting that Shakepeare uses different types of verse to differentiate different types of characters.

William Shakespeare's mythical comedy A Midsummer Night's Dream is known for its use of different types of language. This aspect of the play is used to mark the differences between Athens, which is traditional and rule-bound, and the woods, which is magical and playful. Shakespeare's use of language is perhaps the most effective and imaginative element of the play in how it clearly distinguishes different characters and settings.

For example, lovers and nobility speak passionately and in rhymed verse, seen below:

"Helena: Love looks not with the eyes, but with the mind/ And therefore is wing'd Cupid painted blind" (I.i.245-246).

Fairies use a very specific type of tetrameter. Their language has a light and airy nature, which reflects their position as supernatural beings:

"Puck: When thou wakest, let love forbid/ Sleep his seat on thy eyelid/ So awake when I am gone/ For I must now to Oberon" (II.ii.736-739).

Finally, blank verse is used by the Rude Mechanicals, the ordinary people of the play, to mark their status in contrast to other's. Not only is their speech more plan than the nobles and mythical creatures, but it reflects the practicality of their social position. This is especially evident when Bottom goes into the woods:

"Titania: Thou art as wise as thou art beautiful.
Bottom: Not so, neither, but if I had wit enough to get out of this wood, I have enough to serve mine own turn" (III.i. 969-971).