Shakespeare's Sonnets is the title of a collection of 154 sonnets by William Shakespeare, which covers themes such as the passage of time, love, beauty and mortality. The first 126 sonnets are addressed to a young man; the last 28 to a woman. The sonnets are almost all constructed from three quatrains, which are four-line stanzas, and a final couplet composed in iambic pentameter. This is also the meter used extensively in Shakespeare's plays. The rhyme scheme is abab cdcd efef gg. Sonnets using this scheme are known as Shakespearean sonnets. Often, the beginning of the third quatrain marks the volta ("turn"), or the line in which the mood of the poem shifts, and the poet expresses a revelation or epiphany.