To be glad is to be delighted or to feel joy, delight, or pleasure about something. You can be glad to do something or to see someone because it brings you joy, delight, or pleasure.
Ex: I am so glad to have been a part of the project. It's been challenging, but also brought me joy and many great memories.
Ex: Jan could tell that her husband was glad that his term of Masters study had come to a close. He needed a break from study.
Gladness is the state of being happy or feeling pleasure in something. To experience gladness is to experience a feeling of well-being, satisfaction, or content.
Ex: Each member of the family felt a particular gladness at the reunion. After such a difficult year, the time together brought welcome feelings of joy and contentedness.
Ex: Frederica's aunt experienced great gladness as she watched her niece's performance at the gymnastics competition.
Bright can mean cheerful, happy. It is associated with the ideas of light or shine. For example, a bright smile is one that brings cheer.
Ex: During the young girl's hospitalisation for an appendectomy, she was always cheered up by the bright young nurse who arrived in the afternoons.
Ex: The bright smiles of the young people arriving on campus were always an encouragement to the aging professor at the start of each academic year.
Brightness normally refers to the amount of light there is in a space. If something is described as having the quality of brightness, it is emitting a lot of light. A person that is happy or cheerful could also be said to have the quality of brightness.
Ex: The brightness of the outdoors came as a shock to the boy, who had been up studying for several days in his cramped room on campus.
Ex: One could see the brightness of Madeline's countenance after receiving the compliment of her father on her new dress.