A direct comparison of two unlike things using a comparison word, such as “like” or “as,” for a purpose.
My bounty is as boundless as the sea,
My love as deep…
In this simile, Juliet compares her love for Romeo to the sea directly, using “as.” Her purpose may be to emphasize that her love is limitless and deep, just as the sea is.
A simile, unlike a metaphor, makes a direct comparison, which means that the comparison is expressed explicitly using the comparison word. In a metaphor, the comparison is evident but not explicit. Both devices share the feature of expressing something about one thing in terms of another.