Affect and Effect

If you mean "result," use "effect" (it may help you remember to use effect for result if you think about the "e" the two words share). For example, if you want to talk about the result of a beech tree becoming infected with beech bark disease, you would use "effect," as in, "We are going to study the effect of beech bark disease on this here beech tree." Similarly, if you mean "results," use "effects."

If you're looking for a verb that means "to influence" or "to change," you can use affect, as in "Beech bark disease will adversely affect that tree." However, if you're looking for a verb that means "to cause," or "to bring about," you can use "effect." For example, you might say, "Beech bark disease will effect the death of that tree," meaning that the disease will cause the death of the tree.

As you can see, "effect" can be either a noun or a verb."Affect" is typically a verb. Naturally there is an exception to this rule. In the world of psychology, "affect" can be used as a noun to mean "feeling or emotion or emotional condition," as in "After his favorite tree died from beech bark disease, his affect was very flat."