Hair additions that are secured at the base of the client's natural hair to add length, volume, texture or color are called:

The term for hair additions that are securely attached at the base of the client's natural hair, serving the purpose of enhancing length, volume, texture, or color, is extensions. Extensions can be either temporary or permanent, depending on the method used for application, and they significantly transform the hairstyle by integrating with the client's natural hair.

Extensions are versatile and can be made from natural or synthetic hair, allowing for a wide range of styles and effects. They are typically designed to blend seamlessly with the natural hair, offering a more dramatic look without altering the original hair structure.

In contrast, the other options refer to different concepts. For instance, ponytails are a common hairstyle where hair is pulled back and secured, switches usually refer to pre-made hairpieces or wigs that may not be secured at the base of natural hair, and cascades are flowy or layered styles but do not specifically denote the method of adding hair for enhancing qualities. Therefore, the term "extensions" is the most accurate in this context.