In music:
* A musical chord consisting of three notes. This is the most common usage. Triads are the building blocks of most Western harmony and are typically built in thirds, meaning each note is separated from the next by an interval of a third. There are major triads, minor triads, and other variations.
In other fields:
* A group of three things, especially those that are related or interconnected. This can apply to:
* Literature: A triad of characters, themes, or ideas that are central to the story.
* Philosophy: The triad of thesis, antithesis, and synthesis in Hegelian philosophy.
* Religion: The Holy Trinity in Christianity.
* Psychology: The triad of needs in Maslow's hierarchy of needs.
* Mathematics: Triads of numbers related in specific ways.
* Other contexts: A group of three objects, people, or concepts that are related in some way.
To determine the specific meaning of "triad," you need to consider the context in which it is used.
If you provide more context, I can give you a more specific answer.