Examples of words that can function as a noun or a verb, depending on how they are used, are mail, milk, play, park and walk. These words are pronounced the same regardless of how they are used.
"Mail" as a noun refers to letters and other items delivered by the postal service. As a verb, it is the action of sending something by way of the postal service. The sentence "I milk the cow to get milk for the family" uses "milk" in both ways. In the first instance, it is a verb meaning "express," and in the second use, it is a noun referring to a beverage.
Some words change the pronunciation depending on use. For example, the noun "conduct," meaning "behavior," has the stress on the first syllable. When used as a verb, "conduct," meaning "to behave or manage," puts the accent on the second syllable.