While analogy and simile are both comparisons of two seemingly unrelated things, they are not the same. A simile is a figure of speech, while an analogy is a type of argument; a simile is also a type of metaphor, while an analogy is not. Generally, an analogy is more complex than a simile. Another key difference between the two is that similes in English use either "as" or "like" to make their comparison.
A simile is usually structured in one of two ways. The figure of speech can use the word "like" to compare two items. An example using "like" is, "Her hair shone like the sun." Hair and the sun usually are not considered the same, but the simile describes them as shining in a similar manner. An example of a simile using "as" is, "His teeth were as white as clouds." In that simile, the man's teeth are compared to the color of clouds.
Analogies are used to make a connection between two objects or ideas to better explain the first object. For example, a short type of analogy is, "Coffee is to caffeine as beer is to alcohol." Coffee and beer are both beverages, and caffeine and alcohol are the drugs they contain. In some instances, it may be difficult to determine the connection between the two items.
Another key difference between an analogy and simile is that a simile is a type of metaphor. A metaphor compares one thing to another by stating that the first thing is equal to the second. "Her hair is the sun," is a metaphor, while a simile simply states that her hair shines like the sun.
Analogy and simile also differ in that an analogy can be far more complex than a simile. A writer can craft an entire story as an analogy, while a simile is simply the language the author uses when crafting a story or other piece of writing. An analogy can be more difficult to discern than a simile, as it doesn't have the required "like" or "as."
Analogy and simile further differ in that an analogy can be used to convince someone of something. A person can compare two items when making an argument to prove his point. In some cases, the connection between the two items can be very thin, resulting in a weak analogy. For example, a person may attempt to argue that eating ice cream is the same as drinking milk, as both are dairy products. The analogy ignores the fact that ice cream is higher in fat and contains more sugar than milk.